Clean Master is a utility application developed and updated by Cheetah Mobile. This application allows you to easily clean up parts of your Android phone.
Once you start up Clean Master, you can get information on your phone like how much RAM you are using along with the storage currently being taken up on your phone. This information can help you gauge if you're using too many applications on your phone.
If you believe that you're using too many applications, you'll be able to use Clean Master to help get rid of some of them on your phone through the Advanced Cleaning function.
Overall, Clean Master is a robust cleaning application that might be worth it for your phone but you should watch out for the number of permissions it requires to make it work correctly.