Why com.apple.webkit.webcontent eating 6 Gigs of RAM?

Is this about macOS 12 Monterey where you have posted or about macOS 13 Ventura 13.4 as per your User byline ?

Use the Activity Monitor application and make sure to use View >> View All Processes 

What process or processes are using the Most CPU  and Memory.

Often times - the issue maybe not be one single Process but a combination of Processes

Also, when the computer is using so much Memory - it can be a indicator of a Lack Of Empty Spaces on the Drive.

In which case, the CPU and Memory usage would become Much More because it is searching for Empty Space to save all the Changes the user is performing.

Also, depending on the number of  Open Tabs in your Browser, they can also affect Memory Usage.

Why does it matter how much RAM is being used?

What matters is Memory Pressure. See Check if your Mac needs more RAM in Activity Monitor - Apple Support

Picking up on previous posting above.

RAM will always fill up and empty as the Operations System and Running Applications request more or less Memory.

RAM ( Memory ) is much faster than writing dats to the drive.

Generally, unused RAM ( Memory ) is wasted if not used.

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