When the fermentation is done, it’s time to rack the wine out of the fermentation vessel.
The juice that runs free (without being pressed) is generally considered the purest, highest quality wine. It’s called “free run” wine and is kind of like the “extra virgin” wine.
The rest of the wine is “press wine” and is generally slightly more rustic, with harsher-tasting phenolics.
Press wine is typically blended back into the free run wine. (Remember: the less waste, the better!)
https://winefolly.com/tutorial/winemaking-from-start-to-fini...

Pressing in winemaking is the process where the juice is extracted from the grapes with the aid ... Winemakers often keep their free-run juice and pressed wine separate (and perhaps even further isolate the wine ... very "liquidy" pulps that releases juice easily without needing much pressure that could risk tearing the skins.
https://en.wikipedia.org/wiki/Pressing_(wine)

Red wines are nearly always made from both free run juice and pressed juice. White wines on the other hand are not always pressed. The very best white wines are made from only the free run juice. Historically pressing grapes was done by hand or by people stomping grapes.
http://winemakersacademy.com/pressing-grapes/

Hope it helps!