The term Jujutsu/Jujitsu was not coined until the 17th century. Prior to this is had a variety of different names.
This system of unarmed combat was designed for close combat to defeat or control an enemy similarly unarmed. It involves striking, punching, kicking, throwing, strangling, joint locks and immobilisation techniques. It also involves escapes and counters from these techniques.
Jujutsu first began around the late 1400s and was designed to be used against warriors wearing armour and even armed warriors.
The original form of Jujutsu or old style Jujutsu is known as Koryu Jujutsu. This refers to Jujutsu developed during the 14th to 17th century. These systems were not systems of unarmed combat. On the battlefield the Samurai (warrior class people) would have difficulty using their long weapons (spear, long sword etc) and were sometimes forced to use their short sword, dagger or no weapons (unarmed). The fully armoured Samurai then had to employ his grappling skills.
Modern day Jujutsu is known as Gendai Jujitsu and reflects the fact that we dont have to battle Samurai in heavy armour! Modern Jujutsu has been taken up by many military, special forces, police and security personel. Once again there is now a sport version of the art designed for competitions.