Once you have mastered something, it often seems pretty easy and obvious. Teachers need to remember what it's like to not already know the material they are teaching. They have to constantly remember to put themselves in the shoes of the students. They need to listen to students in order to understand where there are gaps in the students' knowledge, and then they need to present the material needed to fill that gap.
When a teacher does present material in such a way that it makes sense, we may be tempted to take it for granted, but it actually can take considerable effort and skill to put the material together that way. Although I'm not currently a student, people do sometimes try to explain to me how to do things, and sometimes it's frustrating trying to make sense out of their explanations. It's as if someone is giving you directions to get somewhere, and they say, "Turn right at the McDonald's. Three miles before that, bear right at the fork in the road. Before you leave, make sure you bring cash with you because the destination you are going to doesn't take credit cards. After the fork but before the McDonald's, take a left at the third traffic light."
Usually people do give driving directions in order, but when people try to explain other things to me, sometimes I find it as jumbled as this example.
It's a lot easier to understand things if we have a framework to fit them into. I'm bad at understanding mechanical things. Because I can't visualize how the whole thing works, when I learn one piece, it tends to fall out of my brain very quickly because there is no hook to hang it on. In contrast, it's easy for me to visualize connections between people. I am above average at remembering facts about the friends or relatives of people I know because I can envision how those people are connected, and then I can hang the facts on that framework.
When presenting new material, it is helpful for the teacher to present a framework for the information. A single piece of information will make more sense and be easier to remember if the student knows how it fits in to the big picture. It can be a challenge though. The way to help students understand bits of information is to first show them the big picture that it fits into, but the way to help students understand the big picture is to show them the bits which together form the big picture. I think it can be done though. You can start by giving them a general idea of the big picture, and then as you teach each bit, you can talk about how that bit fits with the big picture and with the bits that have been learned before.
