Sometimes people can easily understand each other. For example, if two persons have similar frames to exchange information, they would make fewer mistakes. But if they operate in different frames and have different background knowledge, they may use the same words for different things. In this case they may have difficulties to correctly understand each other.
The second example can be called curse of knowledge, it is a cognitive bias when people mistakenly assume that other people have necessary background to understand them. This may happen when someone starts learning in a new area and asks more knowledgeable person to understand something.
We can even count, how long is the chain of concepts to explain something to another person. For example, our student know only about A, but we need to explain E to him or her. To do that we have to explain B based on A, than C, and D. Only after that the student can understand E.
In the same time we can estimate, how wide is the concept field we need to explain. Let’s assume that we need to explain C to a student who knows about A. It can be a simple case of explaining B before that, but B may be based not only on A, but also on A2, A3, A4 and A5. And to understand C one needs to know also about B2, B3 and B4. But to understand these we first need to explain about more As: A5-A12. So despite the short visible distance between A and C, we have to take into account a wide field of eleven new concepts on the first level and four new concepts on the second level.
Wide field like this can be found in natural sciences. Often a person need wide and deep background knowledge to understand and apply new information. Of course we can optimize studying process if we include only pieces of knowledge that one really needs to understand the final piece.
Please take this in mind when you decide to explain something to another person. Sometimes you need to understand what this person have in mind only to begin your explaining.