Brazilian Jiu-Jitsu (BJJ) is a martial art and combat sport that focuses on grappling and especially ground fighting with the goal of gaining a dominant position and using joint-locks and chokeholds to force an opponent to submit.
A Brazilian Jiu-Jitsu (BJJ) practitioner's gi is similar to a judogi (judo uniform), but is a closer fit. As is the case with judo, the term kimono is sometimes used instead.

While the judogi is regulated and inspected by sanctioning bodies so as to maintain a necessary amount of room between the arm and the sleeve for gripping, and also between the leg and the pants, a BJJ practitioner's gi is not as tightly regulated. The practitioner can therefore benefit from a closer fit, providing less material for an opponent to manipulate.

BJJ is strongly differentiated by its greater emphasis on groundwork.
Brazilian Jiu-Jitsu emphasizes ground fighting techniques and submission holds involving joint-locks and chokeholds also found in numerous other arts with or without ground fighting emphasis.

Submission wrestling (also called Grappling or submission fighting, and technically referred to as submission grappling) is a wrestling style and a general term describing the aspect of martial arts and combat sports (without kimono/GI) that focus on clinch and ground fighting with the aim of obtaining a submission using submission holds.
Same as BJJ, grappling is strongly differentiated by its greater emphasis on groundwork..
The gi form is known for its emphasis on grips using the gi, while the "no-gi" form emphasized body control of the torso and head.