Consider the circuit shown. The LED is now connected to the emitter.
When you now turn the potemtiometer P1, the brightness of the LED follows the potentiometer over a wide area. This is the feature you are looking for in an amplifier.
This circuit is known as the common collector circuit. If you want to understand the difference between this circuit and the common emitter circuit of the last experiment, you should take a look at the topic "Basic Transistor Circuits".
Now you continue with applications in which multiple transistors are used in a circuit...