Progressive overload is usually explained as “add weight.” That is one way to do it and the least available one, because most people run out of plates, space or joints long before they run out of training years.
Overload is a total, not a number on a bar
What a session asks of you is roughly load multiplied by reps multiplied by how hard each rep was. Any of those three can move. Adding weight moves the first. Adding a set moves the second. Slowing the rep down, shortening the rest, pausing at the bottom, or moving the same load through a longer range all move the third.
This matters for anyone training with a fixed load, which is most people training at home. A single weight is not a ceiling. It is one variable held constant while the others move.
The order that works
Change one thing at a time, and change it in this order: reps, then sets, then density, then load. Reps first because it is the cheapest to recover from. Sets next because volume is the most reliable driver of adaptation. Density — the same work in less time — next, because it makes a session harder without making it longer. Load last, because it is the change that most often breaks form.
If you cannot say which single variable you changed this week, you are not progressing. You are just training differently.
When nothing moves
A stall is information. If reps have not moved in three weeks and the sessions feel harder rather than easier, the problem is usually recovery, not programming: sleep, food, or the fact that you added three variables at once a month ago and have been paying for it since.
The fix is almost never a new program. It is one easy week, then the same program with one variable moving again.