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Lens mount
The mechanical and electronic interface where a lens attaches to a camera body and must match it.
The mechanical and electronic interface where a lens attaches to a camera body — examples include Sony E, Canon RF, Nikon Z and the shared L-Mount. The mount handles both the physical coupling and the electronic communication for autofocus, aperture and stabilization. For a lens to work fully it generally has to be made for the body's mount, or be fitted with an adapter (and some adapters limit autofocus or other features).
Concrete example
a Canon RF lens won't natively fit a Sony E body, and vice versa.
What it means when you're buying
the mount is the first thing to check when buying glass, because it determines which lenses you can use today and how easily you could switch systems later — making it one of the most consequential long-term decisions in a camera kit.