It can be a post on Instagram, Facebook, Twitter, TikTok or a story.
The other reason for video trimming is a necessity to show only a short episode to your followers on social media. When you record a video on your camera, some moments can be inevitably spoilt by incorrect focusing, bad light or noise, and other things. If you want to turn your rough material into a good-looking movie, you need to remove all the unusable parts.