you have documentation? lucky you ... Seriously, a 'library' can be anything, from a standard, well document library that comes with the OS, to a chunk of code

you have documentation? lucky you ... Seriously, a 'library' can be anything, from a standard, well document library that comes with the OS, to a chunk of code you got from a coworker. No all of them will have documentation, and then even if you have it it's often the case that the documentation is not 100% correct or up to date.