Q:

Why 'the' in front of a company name

The sentence I have written is "IBM team uses CVS for storing the source code of the project". Should I add "The" in front of the the word "IBM". I am advised to do like that. Is it correct?

A:

Yes in that case you have to use the, because it doesn't refer to IBM but to the Team of IBM, because saying The IBM Team is the same as saying the team of IBM, and here the article the is used because we are talking about a specific team.
Because Referring to Using Articles, Definite Article: "the" section :

The definite article is used before singular and plural nouns when the noun is specific or particular. The signals that the noun is definite, that it refers to a particular member of a group.

For example:

"The dog that bit me ran away." Here, we're talking about a specific dog, the dog that bit me.
"I was happy to see the policeman who saved my cat!" Here, we're talking about a particular policeman. Even if we don't know the policeman's name, it's still a particular policeman because it is the one who saved the cat.
"I saw the elephant at the zoo." Here, we're talking about a specific noun. Probably there is only one elephant at the zoo.

