Checkers is a very old game it was played in egypt over 4,000 years ago whats the pronoun

In the first sentence, both "checkers" and "game" are nouns, right? Person, place, or thing. You can also test for most nouns by putting a "the" in front of it. (Usually not proper nouns.) 

A pronoun is a word that takes the place of the noun so that we are not always speaking only with nouns. How awkward would that be?

What is the word in the second sentence that refers to (in this case) both "Checkers" and "game"?
You could say this, right? — "The game was played in Egypt over 4,000 years ago." But it's smoother to switch to the pronoun here by saying "IT was played in Egypt over 4,000 years ago."