[irunwithmonkeys]

I'm having trouble grasping the concepts of these two reactions.  Can someone explain in simple terms as to how bases have different effects between the two reactions (i.e. KOH, alkoxide, potassium tert-butoxide, etc).  Thank you very much.  I'd really appreciate it.

[Dan]

I'd suggest getting Peter Sykes's "Guidebook to mechanism in organic chemistry" from your library and reading the chapters on substitution and elimination. It is dealt with in all organic chemistry textbooks though, I just like the aforementioned one.
You question is a bit too broad to be answered directly on the forums.

[lakersno834]

in looking at effects of bases in elimination and substitution, a few things should be looked at.  the size of the base is a big one.  if a base is big and bulky, its nucleophelicity (sp?) goes down and it is more likely to  result in elimination.  heat also favors elimination as well.  the size also effects where the alkene will be (bulky = less substituted alkene) in reality with something like -OH, you will probably get a mix of both.