To understand how Brazilian Jiu-Jitsu is different from other martial arts it's helpful to first understand how martial arts differ from one another. We can do this by defining the major martial art categories (there are four) and then grouping each martial art into one of those categories. The categories are:
Striking
Striking styles are primarily focused on using power to throw punches, kicks, knees and elbows designed to inflict damage and eventually knock opponents unconscious. Popular striking styles include Karate, Taekwondo, Boxing, Muay Thai, and Capoeira.
Grappling
Grappling styles are primarily focused on using leverage to control and incapacitate opponents via throws, holds, pins, joint locks, and chokes. Popular styles include Wrestling, Judo, Sambo, Aikido, and of course Jiu-Jitsu
Weapons
Weapons styles are primarily focused on using tools designed to bludgeon or pierce opponents' bodies. Many of these tools have the added benefit of allowing the practitioner to maintain a safe distance from their opponent. Popular styles include Fencing, Kali, and Pistol Shooting.
Combination
While most martial arts have some elements of striking, grappling, and weapons skills, they tend to focus most of their training on only one of those categories. By contrast, combination styles give more equal focus to each category. Popular styles include Krav Maga, MMA, and Hapkido.
The above is a quick simplification to help you understand the major differences between styles. That simplification doesn't fully capture the depth or nuances of each style. If you want to find out more about those styles, click the associated links.
Fun fact: Coach Sean Lynch holds Black Belts in both Taekwondo and Hapkido. Feel free to ask him why he prefers to train Brazilian Jiu-Jitsu.
How is BJJ different from other grappling styles?
We now know that Brazilian Jiu-Jitsu is a grappling focused style, but how does it differ from the other grappling styles?
Wrestling
Modern wrestling is focused on takedowns and pins. Most wrestling takedowns are legal in BJJ and the wrestling singlet is similar to the board shorts and rash guard worn for no-gi BJJ. Wrestling matches can be won by pinning your opponent's shoulders to the mat, so wrestlers tend to be very good at not letting their back touch the mat. By contrast, Jiu-Jitsu is focused on winning by submissions (chokes & joint locks) rather than pins. Jiu-Jitsu athletes are very comfortable having their back on the mat — doing so allows them to use their legs to attack and submit their opponent.
Judo
Brazilian Jiu-Jitsu is descended from Judo and we can trace our belt lineage back to Judo's founder, Kano Jigoro. Judo is most commonly known for it's throws, but Judo competitors can also win by pins, armbars, and chokes, so they have a high level of skill in each of those areas. It's usually easy for Judo players and BJJ practitioners to train with one another since the core positions and submissions exist in both styles. While Judo focuses more on throwing an opponent to the ground, BJJ focuses more on groundwork and submissions.
Sambo
Sambo is a Russian martial art that, similar to Jiu-Jitsu, was heavily influenced by Judo. In fact, one of Sambo's founders Vasili Oshchepkov trained under Kano Jigoro. Sambo practitioners wear a gi top (called a kurta), shorts, and wrestling shoes, so a lot of the upper body gripping techniques are similar in Judo, Jiu-Jitsu, and Sambo. Sambo has a stronger focus on takedowns and leg attacks than BJJ. It's also very common to see BJJ athletes "pull guard" or take the bottom position at the start of a match, but Sambo athletes generally don't concede the bottom position without a fight.
Aikido
Aikido is a Japanese martial art that is primarily defensive. In a self-defense situation an Aikido practitioner's goal is to subdue an attacker without injuring them. Aikido practitioners are known for their throws and joint locks and when training they wear a uniform called an aikidōgi. Aikido is distinct from the other grappling styles mentioned in that it rarely includes live sparring against skilled opponents giving full resistance. Live sparring is a critical component of BJJ training, so BJJ rarely uses techniques from Aikidio because they lack effectiveness against moderately skilled grapplers of other styles.
Brazilian Jiu-Jitsu
The key difference between BJJ and other grappling styles is the refinement and adaptation of techniques so that they can be performed with minimal effort by a smaller, weaker, slower, or older practitioner. Other grappling sports have incredible techniques, but they also emphasize employing those techniques via strength and conditioning. In BJJ, our goal is to be able to minimize the use of strength and conditioning in the application of our techniques. Our philosophy is that if a weaker opponent can successfully perform the move, then it works and will work even better if they have physical conditioning and strength.
If you'd like to get a better feel for Brazilian Jiu-Jitsu's history and culture, check out the Jiu-Jitsu vs The World documentary on YouTube.