Compatible Inkjet Cartridges (aka generic ink) are new cartridges that are not manufactured by the company that made your printer. They are almost an exact replica of an OEM cartridge and generally meet the same quality standards at a fraction of the price. Their use will not void your warranty. In most cases you’ll be able to refill your compatible or generic cartridges once you’ve used them. This can be done using ink refill kits. There are patents protecting many brand name cartridges, so before you buy a printer, think about the cartridges you’re going to buy.
Epson Inkjet cartridges are pretty hard to refill due to the sponge contained in the cartridge. As ink is release (used) the sponge fills with air. Getting the ink back in is a chore, a vacuum pump is needed, you don’t want to know. Purchasing a new compatible cartridge is best when your old OEMs get empty.
Make sure to purchase cartridges that follow ISO standards. ISO standards are a generic name for a series of international quality standards for establishing and maintaining a quality management system. Basically, a quality system is a systematic way of working that ensures consistency, minimizes errors and facilitates improvement.