The Sitefinity CMS L2 cache holds copies of the database content of application objects and complete query results. It is populated during read access and gives fast retrieval of commonly used objects. This way database access is necessary only when the data, which needs to be retrieved is not currently available in the cache, thereby increasing the efficiency and performance of your application. The L2 cache resides in the Sitefinity CMS application process and the cache content is indexed by the object id.
By default, L2 caching is enabled for all persistent types - both in Network Load Balanced (NLB) environment as well as single instance environment. For more information about configuring L2 cache see: Administration: L2 cache settings.