Mobile devices use different types of stored memory to run their processes. Applications store some files (like settings and passwords) in their app cache, to make using the app easier. However, cache storage can be deleted to help resolve performance issues on a misbehaving app, or to speed up your system if your device is running slower than usual and apps are crashing.
The steps to clear the cache on your mobile device will depend on the brand of your device, the operating system it runs on, as well as the version of the operating system. For specific directions on clearing your app cache, and managing your device storage, please find and refer to the resources for your operating system.