How are stock price averages calculated on tickers?

For example: if you glance at google, the 1Y chart of #tsla for February 17th plots it at 208.31 USD.

How is the 24 hour price for 1Y averaged?

Is it a sum of all the daily prices divided by all of the purchases, fed by the exchange data which calculates it?

Do exchanges calculate the stock price with every purchase and spit out a closing price based on all purchase and all volume?