Well the most basic explanation is grappling with the goal of having your opponent submit. How does this happen?
A fighter gets their opponent to submit by using a choke hold or joint lock. Choke hold - Pressure is applied to the neck in an attempt to cut off blood flow to the brain. The goal is to get his opponent to tap out or lose consciousness.
In BJJ training, the “tap” is an automatic stop for all activity. Whenever someone feels danger, the are allowed to simply tap, and their training partner with stop and reset.
This is ensures that all students remain healthy and able to train day after day as well as carry on all of life’s other responsibilities.
Violating the simple rule of “the tap” is a terrible offense worthy of expulsion from the school.