the app cache is the cache in which data is stored that is often needed. however, a lot of data garbage can accumulate here. especially after app updates, it can often happen that an app no longer works properly because wrong data is stored in the app cache. a simple emptying of the cache usually not only solves problems but also speeds up the app every now and then.
Android 10 (One UI 2.0)
Step 1:  Open the  Settings
Step 2:  Tap on  Apps
Step 3:  Tap on desired  App
Step 4:  Tap on  Storage
Step 5:  Tap on  Clear cache
  1. Open the Settings
  2. Tap on Apps
  3. Tap on desired App
  4. Tap on Storage
  5. Tap on Clear cache

Samsung Instructions