the short answer
A macrocycle is the longest planning block in training, typically a season or a full year, built by stacking mesocycles toward a long-term goal. It is the top of the planning hierarchy, above the few-week mesocycle and the weekly microcycle. The macrocycle does not spell out every session a year ahead. It sets the direction and the rough shape of the year, and the blocks below it fill in the detail as you go.
This article is general training education, not medical advice. If you are new to structured training or returning from injury, build up gradually and consult a qualified professional.