Fitbit sells fitness trackers and smartwatches, which are both worn on the wrist. Different uses are best for each one. Fitness trackers are best for casual exercise and general health. Both the Versa 3 and the Sense are full-featured smartwatches that run Fitbit OS, which is an operating system made just for smartwatches. These two watches have touchscreens that work in full color and can show you more information on your wrist.
In the same way, they both have GPS, Bluetooth, and the ability to take calls. Along with mirroring notifications, smartwatches help you use your phone less. Even though the Fitbit Inspire 2 is more of a traditional fitness tracker, the Charge 4 has some smartwatch features, but it doesn't have a color screen or the ability to take calls.