Original Equipment Manufacturer
Original Equipment Manufacturer (usually given as OEM) is a term which has expanded its meaning over time.
The original meaning was just what it says - the original manufacturer of a given piece of equipment. However, it now usually refers to the practise of one organization purchasing products from another, and combining them with its own additions to make a more complex product.
The original organization may sell its products directly to end-users, as well as to other organizations, for use in the latter's products; if so, the latter are referred to as 'OEM sales', or the 'OEM market'.
Sometimes there are slightly different versions of products for the OEM market, often at the buying organization's request; e.g. the selling organization may add the buying organization's name, or perhaps a modification or customization to adapt the item to the buying organization's exact requirements.