Cold Start：A cold start refers to an app’s starting from scratch: the system’s process has not, until this start, created the app’s process. Cold starts happen in cases such as your app’s being launched for the first time since the device booted, or since the system killed the app. This type of start presents the greatest challenge in terms of minimizing startup time, because the system and app have more work to do than in the other launch states.
Warm Start：A warm start of your application is much simpler and lower-overhead than a cold start. In a warm start, all the system does is bring your activity to the foreground. If all of your application’s activities are still resident in memory, then the app can avoid having to repeat object initialization, layout inflation, and rendering.
Lukewarm Start：A lukewarm start encompasses some subset of the operations that take place during a cold start; at the same time, it represents less overhead than a warm start. There are many potential states that could be considered lukewarm starts.