Jenever can be considered the precursor to gin, and although both are distillates (and therefore not liqueurs), there is a definite difference between the two.

Jenever is basically a grain-based distillate, while gin is basically a neutral alcohol-based distillate.

During the distillation process of both jenever and gin, botanicals (of which juniper berries are obviously the most important), herbs and aromatics are added, depending on the desired end product.