After-Hours Market Close

What Does After-Hours Market Close Mean?
The last transaction and final price of a security that is traded in the after-hours market. The after-hours market is generally more volatile than the regular market, but it can give investors an idea of what to expect at the start of trading the next day.

Also referred to as "after-hours close".

Investopedia explains After-Hours Market Close
The percentage of change in the after-hours market is computed by comparing the after-hours close to the market close. If the last price in the market for ABC stock was $5 during regular market trading, this is the opening price in the after-hours market. If the after-hours market close was $10 due to a great earnings release after the market close, the increase expressed as a percentage would be 100%.