Accommodating resistance (AR) is utilized by adding bands or chains to your main barbell movement, which increases the resistance of the load throughout the range of motion. By incorporating AR, you can actually increase the amount of time the bar acceleration occurs, as the bands or chains increase in tension as lifted. This means that as you accelerate the bar to lockout, the tension will prolong the acceleration phase. As that tension grows, it will allow for greater average velocities to be achieved and therefore greater average power output. During a normal barbell movement, you would accelerate the bar from the bottom to the top. As you reach the top, the barbell will naturally decelerate, but AR requires that you continue accelerating to finish and lock out the move, thus helping you to develop and build more power.
As it teaches you to tap into your maximal force production, it helps you to address any sticking points you might have during your barbell movement and even break through plateaus. It is a great tool for power development, especially speed-strength and strength-speed as it calls for more muscle activation. Accommodating resistance also benefits technique development as it requires more control. This will help to ingrain proper form and teach you to stay tight throughout the entire movement.
Additionally, AR can be used for your supplemental movements or added to various dumbbell or body weight movements as it adds extra resistance and calls for increased muscle recruitment/activation. Our muscles experience the greatest amount of tension where the resistance curve is at its peak in the concentric point of a movement. Given that tension is the catalyst for muscle growth, the added tension of AR will place our muscles under more tension, which will provide stimulus for them to adapt and grow.