The learning MORE than you need, so you will remember the bit you need.
Overlearning is the conscious study of something you already know now, to entrain the neural pathways into long term memory. Overlearning is what separates your ability to repeat a nonsense phrase you just heard in 10 years.
Another definition- Ultralearning is that math joke:
You don’t understand algebra until you take geometry. You don’t understand geometry until you take calculus. You don’t understand calculus until you take differential equations. You never understand differential equations.
Overlearning can be applied to any realm of education or technique to further build it into your brain.
A physical analog to over learning is to train your muscles to lift 300lbs now, so that they will be able to lift 200lbs in the future.