Examples are bipolar transistors, field effect transistors etc.

The signal is fed into one connection of the active device and the amplified version taken from another connection.
In a transistor, the signal can be applied to the base connection and the amplified version taken from the collector.

The source of power is usually a dc voltage from a battery or power supply.
 

PASSIVE components do not increase the power of a signal.
They often cause power to be lost.
Some can increase the voltage at the expense of current, so overall there is a loss of power.
Resistors, capacitors, inductors and diodes are examples of passive components.

Integrated circuits contain both active and passive components.
Since they usually increase the power of a signal and require a source of dc power they are treated as active devices.