Conjugate periodization is actually technically called concurrent periodization. The definition of conjugate periodization to mean simultaneously training to raise multiple sub-qualities at once.
A program can mix and match weights/reps in different stages. It combines some heavy lifts for strength, some fast lifts for power, some medium-rep sets for muscle mass, and some high-rep sets for muscular endurance.
This method of periodization was made famous by Louie Simmons, Dave Tate, and the Westside Barbell Club.
This form of periodization would generally be best suited towards the more experienced trainee or athlete.