1. A wrap descriptor embedded in a non-transitory, tangible, computer readable medium, the wrap descriptor defining a set of cards of a wrap package, wherein the wrap descriptor: is a portable data object that enables the delivery of the wrap package to different consuming computing devices over communication networks; specifies a predefined presentation of the wrap package when rendered, the predefined presentation remaining the same regardless of the size or aspect ratio of different rendering environments associated with the different consuming computing devices, the predefined presentation defined by: (i) the set of cards arranged to be browsed in first and second directions in response to navigable inputs; and (ii) each card in the set having a fixed aspect ratio and a fixed relative layout of content, regardless of the size or the aspect ratio of the different rendering environments associated with the different consuming computing devices respectively; and the wrap descriptor further including a plurality of card descriptors, each of the card descriptors arranged to define: (iii) a card component container defining the fixed aspect ratio for the associated card; and (iv) one or more content component descriptors, each content component descriptor defining a content component container maintained at a fixed relative position in the card component container of the associated card, wherein each of the card descriptors and its associated one or more content component descriptors, together, define the fixed relative layout of content appearing within the fixed aspect ratio for the associated card respectively; and wherein, the set of cards of the wrap package, defined by the plurality of card descriptors of the wrap descriptor, includes: (a) one or more cards having a first aspect ratio; and (b) a gallery card having a second aspect ratio that is different than the first aspect ratio, (c) wherein at least one of the cards in the set of cards is a transaction card enabling a transaction for the purchase of one or more advertised items appearing within the card(s) while the wrap package is consumed without having to navigate to a remote website to complete the transaction, wherein each of the set of cards of the wrap package maintains its predefined presentation when rendered on the different consuming computing devices, regardless of the size or orientation of the rendering environment, by scaling the content appearing in each card by the same degree as appropriate for any particular consuming computing device.