In plain English
Instead of checking whether a new request is word-for-word identical to an earlier one, a semantic cache checks whether it means roughly the same thing. AI applications can use this to return a saved response without asking a language model to generate another one, when the match is close enough. Similarity alone does not guarantee that a saved response is still current or appropriate for the user.
Example
A user asks, “How can I reset my password?” If the cache already has a response to “How do I reset my password?”, the application may reuse those instructions if they still apply to the user.