This is a "Matroska" container. It is highly versatile, often allowing for multiple audio tracks (different languages) and subtitle tracks to be toggled on or off.
This is Standard High Definition. While 1080p or 4K is sharper, 720p is often preferred for faster downloads and smaller storage footprints while still looking good on tablets and laptops. ep-5-and0r-s01-720p-hd-desiremovies-skin-mkv
These are "tags" from the group that uploaded or encoded the file. They often add these to identify their specific version of the release. ⚠️ A Note on Digital Safety This is a "Matroska" container