What is the difference between average return vs actual return in the stock market?

Let say that you invest $1000 on the stock market. Someone tells you that you’ll get a 10% average return. 1000×0.10 = $100 profit. So, you have a $100 dollar profit in your investment. Hypothetically speaking you have 1000 +100 = $1100 in total. Now, someone else tells you let me introduce you to my friend call actual return.

You now has to substract any taxes because the government wants his share. You now has to substract any fees, because the brokers or the people that own the platform that you are using to invest needs to eat too. Moreover, you need to subtract any volatility(aka risk) because the market price goes up and down.

So in the end, the actual return you got was about 1-3%, not the 10% from before.