WTF does desu mean?

i see it all over here what does desu mean?

ya mang, >>2 got it right. Literally, it's 'it is'. desuka is 'it is?' or like, just turns it into a question.
ぼこあいぬのくそがです。
I dog shit it is.
I am dog shit.

note: started learning japanese like, yesterday.