The word bipolar consists of two roots - BI, meaning two, and polar, meaning polarities. A bipolar transistor is one in which holes (positive polarity) and electrons (negative polarity) carry the current through the semiconductor forming the transistor.

Two different symbols are used for the transistor.
PNP type having arrow directed towards emitter and NPN type having arrow directed away from emitter.

Schematic name: Q
Before going to the working of transistors, lets go through basics of semiconductors.