How does one delete unwanted extensions?

A Safari Extension? Or a system extension? The reason for asking is that you posted this question in the Safari for macOS forum.

Deleting a Safari Extension is as simple as selecting it in the Safari menu > Preferences... > Extensions and clicking the Uninstall button.

For system extensions, About system extensions and macOS - Apple Support describes what to do about them.

Explain. What is this extension?

Consider using EtreCheck. It will preclude the need to ask additional questions. Old Toad's excellent User Tip How to use the Add Text Feature When Posting Large Amounts of Text, i.e. an Etrecheck Report - Apple Community contains a description and instructions. Be sure to check the box to allow full disk access, otherwise some protected areas of the system won't be examined.

No personal information will appear in the report.