Big Tone Music Brewery
All overdrives are pretty much the same except for slight modifications to 3 tonal parameters: Gain, Timbre, and Symmetry.
Some OD's are high gain that boarder on being a distortion. Some OD's are low gain that act more as a dirty boost to push the front end of your amp. The Gain parameter knob can dial in just the right amount of gain for the drive knob to control.
Some OD's are bright and try to recreate the Fender sound. Some OD's are darker and try to recreate the older Marshall sound. The Timbre parameter knob sets the frequency at which the midrange roll off of the tone knob occurs so you can get the sound of all the other amps that are in between.
Some amps become very compressed at high levels and others have lots of headroom. The same is true for OD pedals. Some OD's have symmetrical clipping and sound very compressed. Some OD's have assymetrical clipping and sound very open. The Symmetry parameter knob lets you dial in the perfect blend of symmetrical and asymmetrical clipping for the exact type of tube tone that you're looking for.
The Boost channel has a Pre/Post switch so you can place the boost either before the overdrive to change the dynamics of the pedal and push it into new sonic territory, or place it after the overdrive for huge amounts of extra volume.