Bands are one way to add resistance and therefore add difficulty to an exercise without adding more weight.
The use of the bands allows a coach to monitor loads while training strength, power, and/or speed.
Bands can be added to traditional lifts such as barbell squats or deadlifts to alter biomechanical advantages.
They can also be used to challenge other exercises such as the 1-Arm DB Bench & 3pt. 1-Arm DB Row which @iammsull is demonstrating.
Content by @scuhlir