I learned Jujutsu and my father was a Judo-ka for many years and showed me the basics. Judo is built upon the foundation of Jujutsu and is a softer art. The big difference between Judo and Jujutsu is Judo is a throwing and sweeping art. All 'fights' end on the ground in Judo, and there are chokes and some basic wrestling submissions, such as ankle locks, shoulder locks, wrist locks, arm locks and wind chokes (sealing the wind pipes). but it was developed as sport (fun fact, it was Dr. Kano who popularized the belt ranking system in Japan).
Jujutsu is older and deadlier by far. It can be considered stand up grappling. Both styles use distraction, angles and leverage to offset the opponent, only Judo seeks to sweep or throw the opponent (like chinese Shuai Jiao) and end the fight either by breaking the opponents skull on the ground (MMA style!) or choking or submitting the opponent once they are on the ground (much like Greco-Roman Wrestling). Jujutsu on the other hand focuses on the limbs of the body (although they do have chokes, sweeps and throws, but not as many as Judo) and strikes. In the higher levels they emphasize pressure points (Kyoshu, most likely taken from Shiatsu- Japanese acupressure) for disabling and even killing the opponent and there are also techniques called Koppojutsu, which emphasizes breaking the joint once it is in a vulnerable position, but this seems to be a rarely taught aspect of Jujutsu, at least in the west. There are soft and hard styles of Jujutsu, unlike Judo which is mainly sport. Jujutsu also teaches the use and defense against weapons. Jujutsu is said to be developed by the Samurai in the feudal days, but it could also (most likely) stem from Eagle Claw Gong Fu, who emphasize 72 joint locks (qi na or tu'i na, is a massage therapy that utilizes acupressure and Jujutsu like holds to relieve stress and blockages in the body, I'm unsure if they are the same) among the various other styles of gong fu that emphasize qi na (usually considered secret techniques in their forms).