Find My lets you track your Apple devices, Find My items like AirTags, and, with their permission, people. You can share location triggers with other people, too, known as geofencing. You can let people know when you arrive or leave at certain locations, including how big the radius is from the location that counts as arriving or leaving.
The reason to do so is primarily safety. With another adult or with a responsible child, you might want them to know you got somewhere you intended to, or if you left a location, they were expecting to find you at. You can also request geofence alerts from someone else, too. They have to agree to provide them.
If you want to know when a kid gets home from school or leaves the house in the morning, Find My notifications can be a perfect tool: enough information but not too much. For instance, a notification whenever your kid arrives or leaves school might set your mind at rest. (And possibly aggravate them no end.)
Read more at Macworld.com