They are referring to "spaced repetition", which is just a method to maximize long-term retention. If you are asked about a concept one day from now, and you successfully recall it, then you are reminded two days from now, and so on.

Thanks, so essentially you set a reminder for you ti sit, and remember what you learned a few days prior?

Yeah. There is software that organises the reminders for you aswell e.g. my company Save All does this https://saveall.ai/

Excellent, thank you.

Basically yes. The exact time isn't so important, as long as the rough interval increases with each success and decreases with each failure.

Brill, thanks for the explanation.