Periodization may seem like an advanced concept but when it's explained it really is quite simple.
So, what is periodization?
Periodization is a way of organising your training. The dictionary definition is "the act or process of dividing history into periods"
And this is exactly what you use it for in training programs, to break down your training to focus on different aspects at different times.
1st training block consisting of 4 weeks:
I might focus on muscle building aka hypertrophy. To do this I might use higher rep sets and have a high overall volume of training.
2nd training block consisting of 4 weeks:
I may then swap focus for the next 4 weeks and lower the reps and us less variation to focus more on progressing the weight on the bar.
3rd training block consisting of 4 weeks:
My 3rd training block may be dedicated to lowering the volume and upping the weights each week to prepare myself to lift a new 1 rep max.
During each of these training blocks you would strive to maintain the progress you made on each aspect while you change focus to the next.
This style of training organisation becomes vital for progression once you reach a certain point in your training and progress slows. The change in stimulas would allow progress to be achieved continuously, it is worth noting that although change is effective you would still keep the training the same during the individual training blocks just Implementing progressive overload between sessions.
If you are stalling and would like further guidance, I will soon be opening up coaching slots for strength and sports specific training.