This has a moderate size and is heavily doped as its main function is to supply a number of majority carriers, i.e. either electrons or holes. As this emits electrons, it is called an Emitter. This is simply indicated with the letter E.
The Base is thin and lightly doped. Its main function is to pass the majority of carriers from the emitter to the collector. This is indicated by the letter B.
The Collector’s name implies its function of collecting the carriers. This is a bit larger in size than the emitter and base. It is moderately doped. This is indicated by the letter C.
As we know that a transistor is a combination of two diodes, we have two junctions here. As one junction is between the emitter and base, that is called an Emitter-Base junction and likewise, the other is a Collector-Base junction.
Biasing is controlling the operation of the circuit by providing a power supply. The function of both the PN junctions is controlled by providing bias to the circuit through some dc supply. The figure below shows how a transistor is biased.