What does OEM mean?

OEM is an abbreviation of 'Original Equipment Manufacturer'.
OEM-products are 'no-name' products which are made by a factory (mainly in China when it comes to microphones), that lets the customer choose whichever brand name they want printed on the products.
Very often, the same products are sold under a lot of different names - and also in group buys under the factory name or without any name.

A few examples of such brand names:
TSM = Swedish distributor Luthman Scandinavia
JJLabs = Swedish retailer chain JAM
GA Projects = Swedish distributor Golden Age Music
T.bone = German retailer Thomann

Some such customers have taken the trouble to make their own website for their brand name - but in most cases it's close to impossible to find any info about the 'brand'.