A Jam Session is a type of musical event where musicians come together to play improvisational music. It usually involves a group of musicians playing together in an informal setting, such as a bar or club. The term 'Jam Session' is derived from the idea of musicians 'jamming' together, which means to improvise and create music spontaneously. A GIG is a PERFORMANCE by a musician or band, typically for a fee. During a Jam Session, musicians often perform without a fee, and instead focus on creating an enjoyable atmosphere for the audience. PERFORMANCE is the act of presenting a piece of music or other artistic work to an audience. During a Jam Session, musicians will often perform their own compositions, as well as improvisations based on existing pieces.