The Structure of the Electric Guitar
The purpose of effectors

There are many types of effectors. Below are brief explanations of some of the major effectors available.

1. Effectors that distort sound: Distortion, fuzz, overdrive
   These effectors are used to produce a strongly distorted sound that an amplifier alone could not generate, or in cases where sound should only be distorted when needed. Distortion and fuzz effectors produce even more distortion than overdrive effectors.
2. Effectors that add reverberation: Delay, reverb
   Delay effectors add an echo effect to sound, while reverb effectors add a reverberation effect. Reverb effects are often built-in to guitar amplifiers.
3. Effectors that expand sound: Chorus
   When applied to clean and undistorted sound, these effectors produce an expansive and beautiful sound.
4. Effectors that cause sound to waver: Phase shifter (phaser), flanger, vibrato, etc.
   Phase shifter effectors produce a sound resembling that of a rotary speaker, while flanger effectors generate a jet sound effect. Vibrato effectors cause the pitch to waver.
5. Effectors with other special effects: Wah-wah, octaver, etc.
   Wah-wah effectors are structured like pedals and when stepped on give the guitar sound a "wah-wah" effect.
   Octaver effectors add a sound that is one octave lower that the source note. Some recent effectors even combine several of these functions.

Equalizers are a type of effector that generally increase (boost) or decrease (cut) certain frequencies in sound. Graphic equalizers feature rows of sliding knobs that correspond to each frequency, while parametric equalizers boost/cut certain frequency bands. When someone is talking about an "equalizer" then are more often than not talking about a graphic equalizer.
Instruments feature built-in equalizers (tone controls), but-with the exception of active type controls-these only cut treble, and are unable to boost at all. Guitarists therefore use effector-type equalizers to gain finer control of their sound.