The FR225 is the evolution of the Forerunner 220. Primarily focussed on running, the Forerunner 225 has a built in heart rate monitor so you don’t have to use a soft strap anymore. It also has an improved interface allowing better focus on your HR-zones. If you have any specific questions, drop them in the comments!
The complete review is available now: https://onemanengine.com/garmin-forerunner-225-in-depth-review/