Blessing in the Catholic Church

In the Catholic Church, a blessing is a rite consisting of a ceremony and prayers performed in the name and with the authority of the Church by a duly qualified minister by which persons or things are sanctified as dedicated to divine service or by which certain marks of divine favour are invoked upon them. In a wider sense blessing has a variety of meanings in the sacred writings:
The Old Testament.
In the morning of Creation God blessed the living creatures that came from His hands, bidding them increase and multiply and fill the earth. When Noah emerged from the Ark, he received God's benediction, which he transmitted through his sons Shem and Japheth to posterity. The Old Testament shows that, in the patriarchal ages, heads of tribe and family seem privileged to bestow blessings, and priests when directed by God, administered it to the people. "Thus shall you bless the children of Israel... and the Lord will turn His countenance and give them peace". The great value attributed to blessings is seen in Rebecca's effort to secure Jacob's blessing for her son. It was regarded as a sure way to secure God's benevolence, peace and protection.
The Catechism of the Catholic Church states, "Every baptized person is called to be a 'blessing' and to bless. Hence lay people may preside at certain blessings; the more a blessing concerns ecclesial and sacramental life, the more its administration is reserved to the ordained ministry (bishops, priest, deacons)" 
Types.
Blessings may be divided into two classes, invocative and constitutive. The former are those in which Divine benignity is invoked to bring some temporal or spiritual good without changing their former condition. Of this kind are the blessings given to children, and to articles of food. The latter class permanently depute persons or things to Divine service by imparting to them some sacred character, by which they are held to assume a new and distinct spiritual relationship, conferring a sacredness so that they cannot be divested of their religious character or turned to profane uses. Such are the blessings given churches and chalices by their consecration.
Theologians distinguish blessings of an intermediate sort, by which things are rendered special instruments of salvation without at the same time becoming irrevocably sacred, such as blessed salt, candles, etc.
Priestly blessing.
"Blessing" in the liturgical sense, is a rite consisting of a ceremony and prayers performed in the name and with the authority of the Church by a duly qualified minister by which persons or things are sanctified as dedicated to Divine service or by which certain marks of Divine favour are invoked upon them.
The adoption of this rite by Jesus and his followers ensured its adoption at a very early stage in the Church's history. Blessings, in the sense in which they are being considered, are entirely of ecclesiastical institution: the Church has confined their administration to those in sacerdotal orders. Priests are ordained ""that whatsoever they bless may be blessed, and whatsoever they consecrate shall be consecrated"." The only case in which one inferior to a priest may bless is when the deacon blesses a candle on Holy Saturday, acting as a deputy and employing incense already blessed by the celebrant.
Some blessings are reserved to the Pope, some to bishops and some to parish priests. The first class includes the right to bless the pallium for archbishops, Agnus Deis, the Golden Rose, the Royal Sword and persons to whose blessing an indulgence is attached. He may depute others to give these. To bishops belongs the privilege of blessing abbots at their installation, priests at their ordination and virgins at their consecration; of blessing churches, cemeteries, oratories and all articles for use in connection with the altar, such as chalices, vestments and cloths, as well as military standards, soldiers, arms, and swords, and of imparting all blessings for which Holy Oils are required. Some of these may, on delegation, be performed by inferiors. Of the blessings which priests are generally empowered to grant, some are restricted to those who have external jurisdiction, like rectors or parish priests, and others are the exclusive prerogative of persons belonging to a religious order. An inferior cannot bless a superior or exercise ordinary powers in his presence. The priest, for instance, who is the principal celebrant of a Mass at which a bishop is present but is not the principal celebrant, is still not to give the final blessing without permission from the bishop.
Efficacy.
Blessings are not sacraments; they are not of Divine institution; they do not confer sanctifying grace; and they do not produce their effects in virtue of the rite itself. They are sacramentals and, as such, they are held to produce the following specific effects:
All these effects are not necessarily inherent in any one blessing; some are caused by one formula, and others by another, nor are they infallibly produced. It depends altogether on the Church's suffrages that persons using the things blessed derive supernatural advantages. There is no reason to limit the miraculous interference of God to the early ages of the Church's history, and the Church never accepts these wonderful occurrences unless the evidence in support of their authenticity is absolutely unimpeachable.
Instances are alleged in the lives of the saints where miracles have been wrought by the blessings of holy men and women.
Liturgy.
Before a minister gives any blessing he should first satisfy himself that he is qualified, either by his ordinary or delegated powers. For the simple blessings of the Ritual, a soutane, surplice, and stole of the requisite colour will usually be sufficient. A clerk should be at hand to carry the Holy Water or incense if required or to prepare a lighted candle. The blessings are ordinarily given in a church but if necessary they can be administered elsewhere and without any sacred vestment.
The Roman Ritual is a treasury of ecclesiastical blessings. The Missal, besides the blessing given at the end of Mass, contains only blessings associated with functions incidental to certain days of the year such as the blessing of palms and ashes. In the Pontifical are found the blessings that are performed "de jure" by bishops, such as blessing persons, kings, emperors, and princes at their coronation and the above-mentioned episcopal prerogatives.
Blessing people.
There is a blessing for the departure and return of pilgrims to the Holy Land, containing prayers and allusions to the Magi's journey, to Abraham setting his face towards the distant land of Canaan and to the Angel companion of the younger Tobias before an appeal to God to send solace on the journey, shade from heat, shelter in storms and a haven of safety.
There follow blessings of persons with Holy Water before Mass, an adult who is sick, a number of sick people, a woman on the approach of confinement and another after childbirth, infants, children come to the use of reason or arrived at years of discretion, children on their presentation in Church, that they may lead good Christian lives and for boys and girls on the Feast of the Holy Infancy that they may grow up to imitate the virtues of the Saviour and reach salvation under His guidance.
Blessings for things.
The Catholic Church holds that things used in daily life, particularly in the service of religion, should be rescued from evil influences and endowed with a potency for good. The principal liturgical blessings recognized and sanctioned by Church are contained in the Roman Ritual and the Pontifical.