It's a slang term, meaning It is great.
The sister of my dad is my aunt
El papa means Potato if there is no accent on the second 'a'. If it is capitalized, it refers to the Pope. It can also be an expression: Es la papa. Then it would mean: It's the best.
"Es interesante la clase" means "the class is interesting" in English.
It is the (of a feminine noun)
This is the life!
"it is the mouth"
"Tu es la ..." means "you are the ...". "Tu es là" (accented "à") means you are here.
It means: It is spring.
What is life?
who is the professor
It means: Is the one.
what is the question?