What is different between level 1 cache level 2 cache and level3 cache?

Caching implemented by the underlying technology is the first level cache. Usually it comes by default with them. For example, hibernate session or HTTP session holds certain objects in the cache.

In addition, if the application enables additional caching by using a caching provider such as ehcache or api available, it will be termed as "second level" caching. For example, in Hibernate, we can use the <cache> element or pragmatically say "query.setCacheable(true)" to enable second level caching.