Seperate from what? I don't really understand quite what you are asking here...
An electric guitar is meant to be played through a guitar amplifier. The typical guitar amp has a preamp stage that brings the signal from the pickups up to line level and allows manipulation of the tone (treble, mid, bass) and often has a way of overdriving the preamp to introduce distortion, and a power amp stage that drives the speakers. Much of the appealing sound quality of the electric guitar is due to the way the amplifier does all this.
You can also plug a an electric guitar straight into a mixer's preamp channel, but this usually sounds pretty dreadful by itself. The reason is that this approach does not allow for all the "magic" that a good guitar amp imparts to the guitar signal in creating the sound that is heard out of its speakers -- it's merely a hi-fi amplification of the raw guitar signal.