People who are good at explaining are almost always smart, but a lot of smart people have trouble explaining things.
One common problem is smart people assuming a certain level of background knowledge, and therefore referencing concepts or using terminology that's not familiar to their audience. It takes some experience to really figure out what vocabulary is appropriate for a particular audience.
I've worked with a lot of fourth graders (10-11 years old). I've seen a lot of people try to explain concepts to them and fail, sometimes because they're using sixth grade vocabulary the kids can't follow, and sometimes because they're using first grade vocabulary and overexplaining things and the kids get bored. It takes practice to explain things at exactly the right level for the audience -- it takes a teacher who is both smart (having mastery of the material) and experienced (knowing what level of complexity is audience-appropriate.)
I remember, I used to be penalized in A'levels if I didn't give examples and analogies when I was explaining a concept. Actually the lecturer never gave any points for technical explanation. But this sort of learning came in handy years later when trying to explain the research I'm doing to my boss and people around me. I just think it is a skill that can be learned.
One common problem is smart people assuming a certain level of background knowledge, and therefore referencing concepts or using terminology that's not familiar to their audience. It takes some experience to really figure out what vocabulary is appropriate for a particular audience.
I've worked with a lot of fourth graders (10-11 years old). I've seen a lot of people try to explain concepts to them and fail, sometimes because they're using sixth grade vocabulary the kids can't follow, and sometimes because they're using first grade vocabulary and overexplaining things and the kids get bored. It takes practice to explain things at exactly the right level for the audience -- it takes a teacher who is both smart (having mastery of the material) and experienced (knowing what level of complexity is audience-appropriate.)