Your average cost per click (aka avg. CPC) refers to the average amount you're charged for a click on your ad.
Avg. CPC is based on the actual cost per click, which is how much you get charged each time someone clicks on your ad.
The actual CPC is what you'll see in your account's "Avg. CPC" column.
You can calculate your avg. CPC by taking the total cost of your clicks then dividing that by the total number of clicks.
For example, if you spent $100 on 25 clicks, your average CPC would be $4.