Just imagine having a large jar with thousands of marbles (genes) of many colors. You are allowed to grab a handful at a time but you must have your eyes shut at the same time.
Your friend will be allowed to do the same. Do you think you both will get all the same colors or will they be different?
This is actually how independent assortment works. It allows for variations in the genes that are in each hand (individual).
Each one of us are not exactly the same. If we were our would not be able to fight off changes in our environment. This could be a rapid rise in temperature or a virus.
When we are different even a little bit some of us will survive to reproduce.
The fact that the jar has thousands of marbles and many colors also increases the variation in the individual. If there were only a a few colors the chance of variation is reduced greatly.
Here is the Punnet square that you most likely are familiar with. Notice that there is VARIATION in the offspring.