Questions about preloading and library items

Hi all,

so I have a few questions about preloading and specifically preloading in relation to items within the library which get added to the stage through AS3.

The main thing I don’t understand is, what is the library? Are these assets contained within the FLA itself and is their data transferred to the SWF on export?

If that is the case, does preloading the entire SWF preload its entire library (even the items that are not on the stage?)

If not, how do I preload items which are in the library?

Thanks in advance!