Have you ever studied something over and over again, but when you took the test you forgot? Meanwhile, there is material that is only explained once but is really easy to remember. It turns out that understanding something does have a big role in the learning process.
If we just memorize, the brain tends to store information without connecting it much with other knowledge. It's different when we really understand. New information can be linked to things we already know, making it easier to recall when needed.
So, when studying, don't just read over and over again. Try to explain it again in your own words, look for simple examples, or relate the material to everyday events. This method can help us see whether we really understand or have just memorized it.
Learning is not a competition of who can memorize the most. What is more important is how well we understand something and can use it when needed.