Logic Pro 9 beginner: get more instuments?

I've been trying to compose some songs with Logic Pro 9 using its software instruments. But I don't seem to have the instruments that the Logic Pro 9 in my college recording class has. My teacher told me that I'm supposed to purchase them in a package or something.

I don't quite understand it. Can somebody please answer some of my questions about adding new instruments to Logic Pro 9? What file format do software instruments come in? And how do I install or upload new instruments into the Logic Pro 9 library? Can they be downloaded? Should I understand things such as VST files, AU files, or plugins? If I should, can somebody explain them to me?

I'm quite a beginner with Logic Pro 9, so I really need the ABCs for getting more instruments to play with. Please help?

Logic uses AU instruments. Pro Tools uses RTAS instruments (in its native versions.)

you can download free plug ins from KVR: Virtual Instruments, Virtual Effects, VST Plugins, Audio Units (AU), DirectX (DX), Universal Binary Compatibility - Audio Plugin News, Reviews and Community

To install new instruments to Logic, go to Macintosh HD, Library, Audio, Plugins. In this Folder is where all your plug ins go.

"Components" are AU Plug ins that logic uses. also here are VSTs, for other DAWs.

just drag ".components" files in this folder, Logic will scan them when you open it up. bang, your done.

if the plug in comes with an installer, always use that.

Pro tools is slightly different, its plug in folder is inside Application support - digidesign (probably Avid now.)

some of the best ones are the TAL audio plug ins. really high quality and free.