Learning is an expanding set of connections held together and supported by a framework of knowledge and experience. Although each student has a unique set of expectations and perspectives, there are also commonalities between people. When communicating thoughts and ideas, it is possible to be misunderstood when someone has a different background or lacks the same experience as the speaker. I'm sure you have all had a funny misunderstanding like this before. The Fifth Dimension song "Age of Aquarius" has been mis-heard as the "Age of Asparagus". To an elementary school student that doesn't know what "aquarius" is or means, asparagus would make more sense!
How can learning be best effectuated by a teacher/ trainer?
A teacher needs to attempt to anticipate areas that could be misunderstood or confusing. When we know the subject inside and out, it is easy to forget that others may struggle at first. We must remember that what we are teaching wasn't always second-nature for us. I had a college statistics class from a teacher whose first language was Chinese. When a question was asked, he was not able to re-phrase or elaborate. He only repeated the sentence that had confused the student and raised his arms like, "What is there not to get?" (That was a long semester due to the language barrier.) Being aware and available to clear up confusion or elaborate is an essential part of teaching.