They fit exactly the same printers — the XL simply holds more ink. If you print often, 202XL works out cheaper per page and means fewer cartridge changes. For light use the standard 202 may be enough. You can run one of each in the same printer without any problem.

The 202XL range includes a photo black alongside the standard black. Photo black is used on glossy and photo paper to give deeper blacks in images, while the standard black handles plain-paper text. Both need to be fitted for the printer to run.

No. The 202XL range uses separate cartridges for each colour, so you only replace the one that has actually run out. A multipack normally works out cheaper than buying four singles, so it's worth a full set if you print regularly in colour.

Keep them sealed in their packaging, upright, somewhere cool and out of direct sunlight. Unopened cartridges keep well for a long time; once the foil is opened the ink can begin to dry, so only unwrap one when you're ready to fit it.