What exactly do mathematicians mean when they refer to "the data" involved in a construction?

I've encountered this many times and I can usually figure out what's going on, but I am curious about the terminology, how it was introduced, and its connotations.

A concrete example: In pages 35-6 of "Differential Geometry" by R.W. Sharpe, there is a section entitled "Construction of Bundles". The author outlines three conditions that hold for a given $G$ bundle, and then later refers to these three conditions as "data" from which a $G$ bundle can be constructed. This usage confuses me.

Is there a semantic reason why standard words, like "component", "part", or "constituent" are not used?

abstract mass nounversion of data. Basically the information that you use as input for the construction. $\endgroup$ – Ryan Budney Apr 15 '13 at 4:30conditions hold. The "set" of data is a bit like a "subset" of some product of "sets". A construction then is like a function from this product to some other "set". $\endgroup$ – Spice the Bird Apr 15 '13 at 4:37