Salutations to you biglight2,
iCloud is a syncing service. What that means is when you record a video on your iPhone using the Camera app, as long as Photos is enabled in Settings > your name > iCloud > Photos then the video will sync with iCloud.
It will then be available on any device that uses the same Apple ID as your iPhone and has iCloud Photos enabled. If the video is edited on any of the devices, it will be reflected on all devices. Similarly, if the video is deleted from one of the devices it will be deleted from iCloud and all devices.
Here’s more on using iCloud Photos - Set up and use iCloud Photos
Thanks.