Final answer:
A tag in cache memory is used to store addresses of data contained in the cache, determining if a data request can be served by the cache or must be retrieved from main memory.
Step-by-step explanation:
In computing, with respect to cache, the term tag refers to a part of the cache memory that stores the addresses of the data that the cache contains.
The tag is used to determine if the requested data is present in the cache (a cache hit) or if it must be retrieved from the main memory (a cache miss).
When the processor needs to access data, it will use the tag to check the cache first. If the tag matches the address of the data the processor is looking for, this indicates that the data is available in the cache. If not, the data will be loaded into the cache from the main memory, and the tag is updated to reflect the new data's address.