Just how it sounds, No gi, or submission wrestling is Brazilian Jiu Jitsu without the Gi (uniform). The lack of friction from the Gi changes the feel of the movement, allowing for more explosivity, athleticism and speed, but fewer obvious grips and handles. There is a greater focus on wrestling takedowns (and adapting our gi judo skills for different grips) , leg locks, and finding control without the Gi fabric to grab onto. Each style stands on its own, or works as a compliment to the other. Learning to escape while wearing a gi makes escaping without one easier, and learning to control your opponent when you don’t have a Gi to hang onto makes control in the gi easier.
method bjj 