Key message: Learning is the acquisition of knowledge or skills.
The German wikipedia presents a simple definition for knowledge:
"Knowledge is usually understood as a body of facts, theories, and rules available to individuals or groups ... (https://de.wikipedia.org/wiki/Wissen, 10.07.21)
What is the difference between theories and rules? In science rules are often called "scientific laws".
"Scientific laws are similar to scientific theories in that they are principles that can be used to predict the behavior of the natural world. ... Usually scientific laws refer to rules for how nature will behave under certain conditions, frequently written as an equation. Scientific theories are more overarching explanations of how nature works and why it exhibits certain characteristics." (Poulsen, T. (2010) Introduction to Chemistry. CK-12 Foundation, https://openedgroup.org/books/Chemistry.pdf, p. 15)
So theories are a combination of rules. To arrive at a simple definition, I define:
Definition: Knowledge is an accumulation of facts and rules.
"An expert [computer] system is divided into two subsystems: the inference engine and the knowledge base. The knowledge base represents facts and rules. The inference engine applies the rules to the known facts to deduce new facts." (https://en.wikipedia.org/wiki/Expert_system, 23.07.21)
"A fact is an objective observation or measurement, verifiable by any trained observer." (Moores, E. M., Twiss, R. J. (2014) Tectonics. Long Grove: Waveland Press, , page 248)
"In the broadest sense, a rule could be any statement which says that a certain conclusion must be valid whenever a certain premise is satisfied, i.e. any statement that could be read as a sentence of the form ‘if ... then ...’ " (Hitzler P., Krötzsch M., Rudolph, S. (2009). Foundations of Semantic Web Technologies. Chapman & Hall/CRC, page 213 - 216)
Rules are conditional statements that state what action will occur when a certain condition is met (if this condition is met, then this action occurs).
Example: When I want to calculate the area of a rectangle, I can use the formula A = L x W. The formula is a rule: If I multiply the length by the width, then I get the area of the rectangle. But that is only possible if I know the values for L and W. The values are facts.
There are three levels of knowledge: surface knowledge, understanding knowledge, and expert knowledge. The boundaries between these three types of knowledge are fluid.
"Biggs (1987) distinguished between three major approaches [to learning], namely deep, achieving, and surface. Deep learners are intrinsically motivated and enjoy exploring the subject matter as much as they can. On the other hand, achieving students are extrinsically motivated and want to do well because of the rewards attached to high performance. Finally, surface learners are interested in learning the indispensable facts only and expend minimum effort to achieve this (Chamorro-Premuzic, Furnham, & Lewis, 2007)." (Chamorro-Premuzic, T., & Furnham, A. (2008). Personality, intelligence and approaches to learning as predictors of academic performance. Personality and Individual Differences 44, p. 1597)
Which approach to learning makes sense is not just a question of motivation, but mainly depends on what goal I want to achieve That's why I changed the names for the approaches.
1. Surface Learning
I have to pass an exam, but I don't have time to study much for it, or the subject is not important to me and I just want to pass the exam. Then surface learning makes sense. I learn all the facts and rules by heart and understand them only to the extent that I can apply them in the situation as required by the exam. I will quickly forget this "surface knowledge" after the exam.
2. Understanding Learning (competence learning)
I need to study for an exam and want to get a good grade. Then I try to understand the subject because I need to be able to apply the knowledge in the exam to several different situations. I will be able to remember this "understanding knowledge" for some time. (If I don't use it again, I will forget it one day.) "Understanding knowledge" is called skill or competence.
3. Experience Learning
When I want to understand a subject deeply, I apply my knowledge of the subject to many problematic situations. After a while, I have gained a lot of experience. I will remember this "expert knowledge" for a long time.
Conclusion: If we understand a subject deeply, we will be able to apply it to many situations and remember it for a long time.