Counters

Counters are units which under fair circumstances win convincingly against another unit. They may win either due to brute force, or by special mechanics. All counters have counters of their own.

Rock-Paper-Scissor
A system of units where one counters one unit and is countered by another unit forms what is colloquially called a rock-paper-scissor counter system. For example, unit A counters unit B, unit B counters unit C, and unit C counters unit A. While the example shows only three units, it is entirely possible that the system has more units. The case for three units is the simplest, since you get only three matchups.