The most obvious difference between Gi and No Gi Brazilian Jiu-Jitsu is the clothing. Gi Jiu Jitsu is the name of a style of BJJ where the grappler wears a gi, which is a traditional cotton jacket with pants and a belt. Gis were worn in BJJ since its beginning in the 1920s, and they are very much inspired by judo gis. However, there are differences between those two, which you can learn about here.
No-gi, on the other hand, doesn’t involve the wearing of the traditional gi, but rather a specific outfit consisting of the rash guard and the no-gi shorts. A rash guard is the top part of the outfit, a garment made of thin, lightweight material, very similar to compression shirts.
Rashguards come in both bold, colorful, and simple designs. Most people prefer to wear rashguards under their gis, as the cloth feels too heavy on the skin, and rashguards help in preventing any possible skin irritation and making you feel more comfortable.
No-Gi BJJ shorts are the bottom part of the no-gi outfit, and they are designed specifically for no-gi. High-quality shorts are made from lycra and polyester, as it allows for more stretching.