Sony used to use two different lens mounts: The A-mount (which is now discontinued) and the E-mount. A-mount lenses can be used on E-mount bodies with an adapter, while E-mount lenses can’t be used on A-mount bodies.  Within E-mount lenses, some are meant for smaller APS-C sensors. They will work on full-frame cameras, but you will need to crop the images as APS-C lenses don’t cover a wide enough image circle. So if you’re buying for a full-frame camera, you’re better off getting Sony FE lenses for full-frame coverage.