What is modulus prescaler?

Some articles on modulus prescaler, modulus, prescaler:

Dual-modulus Prescaler
... A dual modulus prescaler is an electronic circuit used in high-frequency synthesizer designs to overcome the problem of generating narrowly-spaced frequencies that are ... The modulus of a prescaler is its frequency divisor ... A dual-modulus prescaler has two separate frequency divisors, usually M and M+1 ...