All three terms tend to be interchangable.
Distortion is the effect in my eyes, the clipping provided by the circuit is 'distorting' the signal. Overdrive I think comes from how old amps would distort the signal by the user 'overdriving' the tubes, because of the nature of the act in the early days, the result was usually fairly low gain.....hence lower gain pedals being referred to as overdrive as opposed to distortion, which often relates to higher gain circuits. Fuzz tend to be more saturated, with mid cuts, sometimes more squarewave sounding.
All of these overlap at some point with some pedals having multiple mods, options, gain stages, clipping options etcetc.
Its all about what sounds good to your ears in the mix
Si