OEM stands for Original Equipment Manufacturer, or "Original Equipment Manufacturer", in Portuguese. OEM are products made especially for large companies, they are not intended for the final consumer and therefore generally have a much lower cost than those found in stores.
Products that carry the OEM seal are sold to specific companies that assemble the final product, such as Dell, HP, Positivo, etc. Many OEM products do not come to the consumer with the seal of the company that produced them, but with the brand that finished the product.
Many people choose OEM products because they have a differentiated value, but the entire assembly process has to be carried out by a reputable company, since the product is not seen in the box, it is already out and has been installed.
For the products to be so cheap, large companies purchase them in large quantities, in addition to having their own contracts of product licenses, such as Windows, Office, among others, as well as hardware devices such as motherboards, processors etc.
OEM software
There are also OEM software, which is software that Microsoft sells to computer companies for a much lower price than what they sell to end consumers, like Windows, motherboards etc. These systems reach the consumer when the computer comes from the store with the software pre-installed.