OEM means "Original Equipment Manufacturer." In industry, it means when a company sells a product as if it was their own (their own branding, packaging, etc.) but it is actually made for them by another company. In an OEM situation, the first company typically prepares a simple specification/sketch of what they want, not a detailed drawing package. The second company then does the detailed design work, makes some prototypes, takes the protos to the first company for approval, makes any requested changes, etc., and then manufactures the product, packages it, and ships it to the first company which sells it as if it was its own product. The second company manages the whole engineering and manufacturing process.
This is as opposed to a contract manufacturing relationship in which the first company does all of the detailed design work and then sends the complete detailed drawing package to the manufacturer who manufactures the product exactly as specified and ships the finished goods to the first company which sells it.
The real test comes when the product doesn't work. In the OEM relationship, the second company, the manufacturer, is responsible to figure out the problem and fix it; they are responsible for the design. In the contract case, assuming that the second company is following the prints exactly, it is the first company's responsibility to figure out why the design isn't working, change the design, redo the drawings, and send the corrected drawings to the manufacturer.
Of course, companies are free to negotiate any type of relationship they want and actual deals are often somewhere between these two classic arrangements.
In the case in question, since this wire-stripper multitool is unlike anything else Copper Tools makes and since I doubt that Copper Tools really wants to get seriously into the multitool business, I suspect that they just made a quick sketch and took it to one of the off-shore companies that's knocking off the PST right and left and said, "Can y'all do some'in' like this for us?" And they entered into an OEM agreement.
