Say-Express in words. a statement.
Tell- to make known.
I told him not to repeat it . You made it known that he should not repeat it.
It's-Contraction of It is and it has.
It's raining.-It is raining.
It's been said.-It has been said.
Its-possessive pronoun.
Hockey has lost its glory in India.
I have joined a short term course. What is the duration of the course?
Pot belly.This word is commonly used here.
Regards,
rj1948.

Student or Learner