RandomInteger is a command that produces a random number from 0 to 10.
Now evaluate this command:
myRandomNumber = RandomInteger
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.
myOtherRandomNumber := RandomInteger
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.
yes there is, the := notation reevaluates the right-hand-side each time it is evaluated. So there is a difference between these two definitions: