it is a conventional junction-isolated bipolar IC technology to make a stable low voltage reference and also provide a local bias that is not adversely affected by the ambient noises or transients.
A generator of reference voltage (to be used as a voltage source) that is based on the bandgap (1.11 Volts for Si). They are considered as fundamentally stable voltage sources, not affected by external factors (temperature etc).
normally when we make a power supply the o/p voltage or current doesn't sustain with aconsant value which it should be. this because of mainly temperature chaging makes the transistor unstable. so, the reading ae not correct at that situation so, a temp. compensation ckt is built within the power supply itself.