Educators demonstrate a broad knowledge base and an understanding of areas they teach.
Something I heard experienced in high school profs that I (thankfully) didn’t have was this tendency that when someone was confused and asked a question about an element of the contents of a lesson was either repeating the book definition or “look it up on the internet”. Now autodidact-ism is something that should be supported where students show a desire and capability but it shouldn’t be a requirement for learning. It would be much better to have someone who is particularly educated in the subject to be able to explain and help the learning along, that’s why we have teachers.
So the teachers need to know about the things they teach. Obviously.
Unfortunately learning is not equivalent to downloading a file off the internet, it takes patience and time. There are some few university teachers I have encountered who were scarily intelligent and loved learning enough that they were able to spend a month learning an unknown subject to the point they could teach it the next semester.
We new teachers are not those people.
Fortunately a broad knowledge base can be supplemented by humility and research, though the skills that you develop can seem like they are less than they actually are.
I have never thought that I was particularly knowledgeable about computers until I joined the BEd program. When I look at what I can do I think I am average, almost like a reverse Dunning-Kruger effect.
https://thedecisionlab.com/biases/dunning-kruger-effect
I know some Computers, some Math, some English, etc. but I also know something else. I know that there are many people who can outclass me in understanding of any one field and, to be completely honest, in more or all of the different fields. What this standard asks for is a broad understanding and not necessarily the deepest one. I don’t need a deep understanding of Field theory like a physics major to understand that graphing has purposes in jobs and everyday life that makes it something that grade 6/7 students should probably at least dip their toes in. If they get the exposure to it then when they see a job they like that needs it they can get the deeper knowledge then. But without the broad knowledge that a teacher has students are less likely to trust the “I know people use it but I can’t think of an example”. This example was from a class that I happened to observe, and I was able to chime in about its use in gaming, forestry, and the general understanding of how spacial awareness works.
The particular knowledge builds rapport with students. If they trust that you know things they will be more willing (not guaranteed) to listen to the things you say.
A broad knowledge base also helps you sift through the torrent of available resources. Unlike the past there are near infinite resources available and some of them are not obviously useless until they are tried. You need the discernment to find these things and without it your work will be less effective and take more time. Sometimes you can get away with that extra time, but then the time needs to be made up in other subject areas, so you at least need to start with knowing something or else your learning process will be at the cost of at least one class of student’s learning.