Boiv, Bois, Boit.
What's the difference?
"Bois" and "boit" are different present tense conjugations of "boire"--"to drink." Here's some more information about conjugation: http://www.laits.utexas.edu/tex/gr/v1.html and here's the full conjugation of "boire": http://french.about.com/od/verb_conjugations/a/boire.htm
"Boiv" isn't a word in French, but "boivent," which is pronounced "boiv," is another present tense conjugation. (The -ent ending on conjugated verbs is never pronounced.)
"Buvez" is also a present tense conjugation--the "vous" form. Some conjugations in the imperfect are also pronounced similarly but spelled differently: "buvais," "buvait," etc. But if you're following the skill tree you won't get to imperfect for a while, so don't worry about that right now. Hope that helps! :)