First level cache
Second level cache
Note that the query cache does not cache the state of the actual entities in the result set; it caches only identifier values and results of value type. So the query cache should always be used in conjunction with the second-level cache.
Let me reiterate that Hibernate is *not* holding on to actual instances of the objects. Why is this important? Two reasons. One, Hibernate doesn’t have to worry that client code (i.e. your code) will manipulate the objects in a way that will disrupt the cache, and two, the relationships and associations do not become ‘stale’, and are easy to keep up to date as they are simply identifiers. The cache is not a tree of objects, and can instead just be a conceptual map of arrays.