It’s really a difficult task to narrow Jujitsu as a particular style. The problem with it is that it’s the root of several different styles of combat. While the techniques vary, the essence of it remains the same.
Jujitsu was a style of combat originally founded by the samurai. Ultimately, the goal was to enable an unarmed and unarmored combatant to be able to take on a fully armed and armored samurai. From this essential philosophy, several systems of combat have been founded.
The essential style of Jujitsu is to use attacks and defenses that negate the advantage of another opponent. Originally, it was about the bare-handed warrior being able to take on a fully armed opponent. Consequently, its primary focus was on throwing techniques, pinning, and joint locks that used the aggression of the opponent against him.
At one point in Japan’s history, it became illegal for samurai to stride around fully geared for combat. This led to a style that disregarded the question of armor called Edo Jujitsu, which added the element of striking vital parts of the opponent, leading to the legendary Kyushojutsu, aka Dim Mak or Death Touch techniques.
Since then, Jujitsu has evolved into several different styles, some of which maintain the name of Jujitsu. Judo is an offshoot of this style, as is Brazilian Jujitsu. All of the newer schools of fighting maintain the old way of thinking: An unarmed combatant can take down a fully armed opponent.
Judo excluded for the most part, the newer variations on Jujitsu (or more accurately, Edo Jujitsu) have grown to incorporate kicks and punches and weapons. One little known weapon is the hojo cord. The use of the hojo cord was developed for the Japanese police for when they deal with a particularly awkward situation. Japanese tradition held that accused, but not convicted, prisoners cannot be bound by a rope tied in knots. Until relatively recently, the Japanese police force used rope to bound their prisoners. This led to a particular style of Jujitsu and rope binding called Hojojutsu, which involved binding prisoners without knots.
Ultimately, the problem for the lay person in learning jujitsu is that it takes many years of practice and training to be proficient at. Most people don’t care to wait that long to be good at something, and all the classes leading up to being “good” don’t mean anything if you’re attacked now.