"Restart" is found on your Fusion, under apps > settings , and will simply power your Fusion off and back on.
"Factory Reset" is found on your Fusion, under apps > settings , and will delete all the recorded data on your Fusion (data already synced to your phone will remain on our servers linked to your account) and restore it to factory settings. Your Fusion will display a 4 digit pairing code (and/or "striiv.com/start" and battery %) as it did coming out of the retail box. After doing a Factory Reset, you'll have to re-pair your device to your phone.
To do a Pin Reset, place your Fusion back into its charging cradle. Flip it over and use the end of a paperclip to hold down the tiny button marked "Reset" on the back of the charging cradle. This is essentially another method to restart your device.