#2
There's a whole range of different woods that guitars are made of, no wood is better than another. Just depends on what sort of sound you want.
#3
Alder: Mostly used by Fender, has a brighter tone, good sustain.

Basswood: Lighter than mahogany, balanced tone, used by Washburn mainly. Said to be less durable than the others.

Mahogany: Warm tone, not bright as Alder, mostly used on Les Pauls, gives them their long sustain. Used by Gibson,Ibanez.

Ash: Mostly used by Fender on guitars with natural finish.I heard good things about natural Teles but never played one, so i can't provide anything here.

But if you ask me, the main thing to consider is not the type of wood but the quality of the guitar. Cheaper Washburns are made of Basswood, but so are high end Ibanez-RG's. First consider which type of guitars will fit your music style, then consider the brands and their models, the choice of wood should be the last consideration,if necessary imho.