JPA implementations have "managed entities", sometimes called session or 1st level cache which is making sure that every entity is loaded at max. one time within a transaction. Like e.g. checking user/user permissions is something which typically has to be done in several places in course of a single request - you don't want to keep loading them for every check, you don't want to keep passing them across 20 layers, so some form of caching is needed. JPA implementations do it for you automatically (assuming you're fine with transaction-scoped cache) since this is such a core concept to how JPA works (the fact it's also a cache is kind of secondary consequence). JPA implementations typically provide more advanced caching capabilities, caching query results, distributed cache (with proper invalidation) etc.
wesselbindt|1 year ago