A cartridge oil filter lacks the metal shell case common to oil filters, as the shell is part of the vehicle. In order to replace these filters, you have to remove the casing to expose the filter element, which will stick to the case or the filter mount on the engine, depending on the design.
Example: 2007 Volkswagen Rabbit 2.5L
On this example, the oil filter can be accessed by getting under the engine, removing the underbody panel, releasing the oil suction, and removing the shell.
Example: Dodge 3.6L VVT
In this engine, the oil filter is accessed from the top, making it a little easier to work on.