It was heavily used in the early-to-mid 2000s for storing low-resolution, low-filesize videos on phones, often referred to as "3G video" 1.
This container format was designed to allow mobile phones to record, store, and transmit audio and video files over high-speed wireless networks 1 . k.109.3gp
If you need to edit or share it, it is recommended to convert the file to a modern format like .mp4 using an online converter or free software like Handbrake . If you can tell me: It was heavily used in the early-to-mid 2000s