(Original Equipment Manufacturer) The rebranding of equipment and selling it. The term initially referred to the company that made the products (the "original" manufacturer), but eventually became widely used to refer to the organization that buys the products and resells them. However, the OEM reseller is often the designer of the equipment, which is made to order.
Added Value or None
The reseller often does not add extra value to the equipment, but merely brands it with its own logo. The reseller's name is either placed on the devices by the contract manufacturer that makes the equipment or by the reseller itself. However, a reseller may indeed add value. For example, it might purchase a computer, add its own hardware and software and sell it as a turnkey system (see VAR).
There are numerous companies that specialize in OEM manufacturing and never sell anything under their own brand (see contract manufacturer). Many companies do both. They manufacture and sell retail, but also have a separate OEM division for goods that are private labeled.
In the case of online vendors OEM often refers to a plain version that does not come with any extra's. The OEM version of the Samsung 470 does not come with any drive bay adapter, cables, a cd-rom disc with cloning software & utilities, or free game. The retail versions of the Samsung 470 usually come with one or two of the extras. The extras can vary by model and sales promotion.
I purchased the Samsung 470 256GB OEM version. It did not come with any extras. That was okay with me. All I wanted was the ssd.
You can install any version of Microsoft Windows 7 you want. You are definitely not restricted to an OEM version.
BTW - You can download the latest version of the Samsung SSD Magician utility for free at the Samsung web site. It takes care of SSD and Windows optimization.