RandomInteger[10] is a command that produces a random number from 0 to 10.
Play around with myRandomNumber. How does myRandomNumber behave? myRandomNumber is always the same number. The right hand side of the equal sign was evaluated once and became the value for myRandomNumber.
Play around with myOtherRandomNumber. How does it behave? myOtherRandomNumber is always a different number. The right hand side of the equal sign re-evaluates every time you call myOtherRandomNumber.