What is the meaning/use of "hu" or "ho"?

In the first conversation lesson, you learn that one response to "How are you" is "Mai achhi hu" (female). But the meaning of the word "hu" is never explained. I have heard "hu/ho" used in sentences but don't know what it means. can someone help? :)

"Hu" translates to "am" in this case, but it is not always this way in every sentence. "Hu" can also be used as an end marker of a sentence.