Okay, imagine you are in a school and you want to change classrooms to another school. Transfer admissions is like changing classrooms, only it's for college.
Let's say you start college at School A but then you decide you don't like it there and want to go to School B instead. To do that, you need to apply as a transfer student to School B.
When you apply as a transfer student, you still have to meet certain requirements. Just like how you need a backpack and pencils to go to school, colleges have their own requirements for transfer students. You'll need to show that you've done well in your courses so far and that you've taken classes that are similar to the ones at School B.
Once you get accepted as a transfer student, you become a student at School B and take classes there. It's kind of like if you go to a new classroom, you start learning new things from a different teacher.
So transfer admissions is just like changing classrooms in school, but for college. You have to apply to a new school, meet certain requirements, and then start taking classes there.