Question on yeast

I have wanting to try some recipes that I have collected here and there and the one thing that I'm confused about is the difference between the types of yeast.  All I have used is the ones in the little packets and that's mostly for convenience.
Can anyone tell me if a recipe calls for 1tbls. of yeast is this equivalent to one packet?  And whats the difference between the packets and the bottled forms of yeast?

Arigatou gozaimasu!
(Thank you very much)
mangaholik :o)