Cheesecake is not really technically a cake although it's called a cheesecake.
In reality a Cheesecake is more of a pie than a cake although a Cheesecake does share some similarities like being a baked desert.
The cheesecake's structure and ingredients, and most particularly the creamy cheese based filling and often a crust of a cheesecake actually differentiate it from a regular and typical cake.
As a result of this the cheesecakes are more closely related to pies or even tarts instead of a cake.
When it comes to what qualifies as a pie, the pies are defined by their crusts.
For example a filled pie (also single-crust or bottom-crust), has pastry lining the baking dish, and the filling is placed on top of the pastry but left open.
A top-crust pie also has the filling in the bottom of the dish and is covered with a pastry or other covering before baking.