the Mobile SDK “Profile” extension is a client-side key/value store on the device.
It acts as local store for user profile data cached on the device by the Mobile SDK. (e.g., loyaltyTier, plan, hasOnboarded).
You can use them in rule conditions or data elements in Data Collection (Tags) to inject the addition user attribute them into the XDM sent with Edge.sendEvent(...).
Some of the API methods are deprecated refer the details here https://developer.adobe.com/client-sdks/home/base/profile/api-reference/