Entities are used to describe types of information, while Maltego does come with a number of pre-configured entities there may be cases where you want to create your own entities. These cases could be because you are simply building up a mind map of offline information or that you have developed transforms for a type of information not covered by the default. Before re-inventing the wheel by create entities that already exist, have a look at the Entity Reference Guide for all the standard entities that are included in the Maltego client. CaseFile comes with a lot more entities than Maltego that are generally used in law enforcement type investigations. These entities do not come with any transforms but can still be installed to your Maltego client from the transform hub.