They're two entirely different things. An average--also known as the mean--is calculated by adding all the numbers in a given set together, and then dividing by the number of items in the set. For example, if you asked, "What's the average price of a 2 bedroom condo in my building?" and there had been four recent sales--at $140,000, $160,000, $180,000, and $200,000, I'd add those together--coming up with $680,000, then divide by 4--yielding an average of $170,000.
Percentage is the relative gap or difference between two numbers. If I were selling that $200,000 condo, and the real estate agent said his/her sales commission was 6%, then I'd owe the agent $12,000. Put another way, $12,000 is 6% of $200,000.
Hope that helps.