What's the meaning of the expected value?

An intuitive explanation

I was using the concept of expected value long before I understood anything about probability theory.

Back in high school, I was a fan of no limit Texas hold’em, and I quickly learned the concept of pot odds. Say, if I would win the hand with 10 cards and would lose with the remaining 40, I should only call a bet if it is not larger than the quarter of the current pot.

This is called positive pot odds.

Positive pot odds

Why should you only play with positive pot odds? Because on the long run, such calls are profitable; others are not.

Fast forward a few years. Instead of playing poker, I am sitting in my introductory probability theory class as a math major, and the teacher explains us the expected value.