Getting specs for all hardware

Does anybody know how the big retailers get all those detailed specs on every piece of hardware they sell? Do they have a huge team of people looking the information up on the manufacturers' websites or do each of the manufacturers send the specs directly into the retailers database system?

I want to be able to get all the specs for hardware (like newegg has on their product pages) for most of the hardware of the last 5-10 years and immediately when new hardware comes out.

How does anyone even learn when all these thousands upon thousands of manufacturers come out with a new product?