Is it comatible with multiple devices?
For example, can I use it on my xbox one day then use it on my laptop later?
No.
In order to use the external on a 360/ONE, the HD must be reformatted. This should then NOT be able to be used on a computer until it is again reformatted for whatever platform (ie. Mac/Windows). It also should NOT be able to be plugged into a 360 if it was formatted for the ONE.