What is the difference between the UJT and BJT transistors?

UJT (UniJunction Transistor): It is a transistor with only one junction and three terminals: an emitter (E) and two bases (B1 and B2).

BJT (Bipolar Junction Transistor): This type of transistor consists of two junctions and three terminals, namely Emitter "E", Base "B" and Collector"C". There are two types of BJT, i) PNP and ii) NPN.