Difference between plain switches and switch panels:

A plain switch has only two possiblities: on and off.

With dimming switch panels:

Intensity of the light can be varied.
The rate at which the light turns on/off can be controlled.
You can create scenes.
You can dim or fade into any scene and the rate can be varied.
Your favourite settings are stored.
Dimming prolongs bulb life.
Dimming saves electric power.