Teach 3 and Teach 4 usually go hand in hand. If you are providing multiple ways for students to engage with content, then you should be engaging them at all learning styles with appropriately challenging work.
I remember years ago someone telling me that everyone learns at his or her own pace and that really stuck with me. Some students are quick to pick up on things and some are not as lucky. This means that you as the teacher should be able to challenge the students at these different levels. Getting a lower learner to learn the basic information you are trying to teach may be a challenge to them, but what about those students that have already nailed the objective and are ready for something more? This is the challenge! What are you going to do that will push these students over here while at the same time giving these students over here appropriate challenging work?
What does TEACH 3 look like in your classroom? Well a level 3 teacher will have ALL students engaged with the content and activity you have planned. The work will be differentiated in order to meet each learner. It will be appropriate and challenging in order to take them from where they currently are to the next level.
A level 4 and 5 teacher will make sure they are working together, having accountable talk within their group, and making sure they are moving beyond their current level of knowledge.
Let's say that your teaching 1st grade math and your objective is getting students to solve basic addition problems up to 10. You may have lower students that are having trouble counting and putting the numbers together. You may have students that are on target and having minimal trouble, but individually double checking, correcting themselves, and solving the problems on their own. You may have student that are ready to solve double digit numbers because up to 10 it is too easy for them. In this scenario, your classroom should demonstrate each of these groups of students set up with different activities during this lesson that allow them to demonstrate understanding of the objective, but pushing them at different levels in an engaging way so that they are not bored and always interested in the activity they are performing. It is challenging and appropriate within each group, but at the same time focusing on the objective. This way, you are meeting all students at their individual learning levels but pushing them at the same time.
We do not want students only "remembering" or "applying", but being challenged. This is where having high expectations for your classroom comes in. You would be surprised at what students can do when you simply challenge them.