The term describes the number of details in a picture. In the case of video files, one speaks of either lines or pixels. In analog TV video playback, the resolution is the number of vertical lines; in digital video files, the resolution is the number of vertical and horizontal pixels. The higher the resolution, the more details can be stored in an image or video. Typical resolutions are:

333x480 VHS

768x576 PAL

720x576 DVD

1280x720 Blu-Ray

1920x1080 Blu-Ray

3840x2160 4K

7680x4320 8K