To understand something it is not enough to merely perceive it, although noting the existence of that something, ought to be part of it. Something can be an idea or an object, in other words mental or physical. Let’s consider the case of objects first.
To fully understand something you have to know what it is and also where, when, how and why it is. The latter amounts to grasping the reason for its existence. What it is, is a matter of identification and definition. It amounts to correct categorization. Where and when is a matter of locating it in spacetime.
One could see an object and practically immediately state with some certainty that this is a radio. You have perceived it and could place it in a category of things already understood to some degree. To some degree, is stated advisedly as one could categorize the object correctly without understanding how it actually works which would be part of full understanding. Thus we have degrees of understanding. Full understanding would embrace all the constituents listed in the second paragraph above.
Concepts and percepts
There are concepts and percepts (sense messages). We can’t have percepts without concepts, we can’t have percepts without communication, we can’t have communication without space. Something like ‘honesty’ is a concept, not a percept. You can try as much as you like but can’t really see ‘honesty’. If we could our world would have looked differently. Without the concept of space, there would be no percepts. Thus concepts are senior. Percepts have a mechanical communication aspect and concepts do not.
Concepts can exist independent of observation, whereas percepts are the direct result of observation. So we might say that there are two types of understanding, a priori understanding and a posteriori understanding.
Understanding ideas
In the case of ideas the matter is simple. The only requisite to understanding ideas is to be able to define them and relate them to other ideas. One might say as Hubbard did that the degree of understanding depends on how much relationship one can give it to other ideas. {EVALUATION OF DATA, a datum is as understood as it can be related to other data. (SOS Gloss)}
ARC and experience
Experience is defined (Merriam Webster) as the act or process of directly perceiving events or reality.
When you experience something you are at the effect end of a communication. You duplicate whatever was steered in your direction. Experiencing life and things involve ARC. Hubbard defined communication as the operation, the action by which one experiences emotion and by which one agrees. In another context he defined it as the interchange of perceptions through the material universe between organisms. Experience thus can be considered, the duplication of that which emanated from the source point, but it is more than that. The experience also implies that you have an attitude or a feeling about that what’s been duplicated. Also the fact that you may agree or disagree with it plays a role. So here we have it A+R+C=Experiential Understanding one could say. Not necessarily conceptual understanding, quod erat demonstrandum. ARC does not always equal understanding.