Theb is a multipurpose word. It can be used as virtually any part of speech (though the noun form is not very common). Grammatically it is very similar to how "fuck" is used, except theb can also be as a substitution for "reaction" words such as "neat" "cool" or "lol" etc. May also be used as a greeting or exclamation in certain contexts.
What the theb is going on here?
That's pretty theb brah.
Theb! (as in "lol")
Theb it.... (as in "God damn")