In cell phones and networks, a cache usually refers to a memory storage area in the phone or network that stores copies of information that is likely to be needed in the near future, so it can be accessed faster.
For example, when you visit a web page on your phone, a copy of the page may be stored in the phone's cache memory. Then if that page is requested again, it can instantly be displayed from the cache, instead of waiting for the page to download from the Internet again.
Data in an electronic cache is therefore just a secondary copy of data, created for faster access.
Software manages the cache to insure data is accessed from the fastest place and cached data is not outdated. But in some cases, data in a cache can become corrupt or outdated anyway. Clearing / deleting the cache can fix such problems. Because it is not the original/primary copy of the data, cache data can be deleted at any time. When that data is needed again, software will automatically fetch the data from the original/primary source if it not found in the cache.