What are undefined objects in Euclid’s geometry?

What is the difference between an axiom and a postulate?

Give an example for the following axioms from your experience:

(a) If equals are added to equals, the wholes are equals.

(b) The whole is greater than the part.

What is the need of introducing axioms?

You have seen earlier that the set of all natural numbers is closed under addition (closure property). Is this an axiom or something you can prove?