What's the difference between SRAM road groupsets?

Like its main competitors Shimano and Campagnolo, SRAM has a hierarchy of groupsets with levels offering different weights, number of gears and - of course - prices!

Whilst Shimano and Campagnolo have been producing bike components since the 1920s and 30s, SRAM was only founded in 1987. However, although much younder it has become know for pioneering innovations such as 1x road drivetrains, wide-range cassettes, and wireless shifting.

I will try to keep this groupset list current, please give me a shout if I mess up!

Weight(g) Brakes Rear sprockets* Chainrings  Low sprocket max teeth** Electronic
RED eTap HRD 2361 Disc 11 2 32 Y
RED eTap 1750 Rim 11 2 32 Y
RED 22 HRD 2119 Disc 11 2 32 N
RED 22 1741 Rim 11 2 32 N
Force 1 2466 Disc 11 1 42 N
Force HRD Disc 11 2 32 N
Force 22 2097 Rim 11 2 32 N
Rival 1 2690 Disc 11 1 42 N
Rival HRD Disc 11 2 32 N
Rival 22 2348 Rim 11 2 32 N
Apex 1 2719 Disc 11 1 42 N
Apex HRD Disc 10 2 32 N
Apex 2419 Rim 10 2 32 N

* the more spockets, the smaller the jump between adjacent gears.
** the more teeth, the easier the bottom gear will be.