A certified teacher is an adult who has completed a special training program to learn how to teach kids in school. Think of it like your mommy or daddy going to school to learn how to be a really good teacher so they can help other kids learn and grow.
Before someone becomes a certified teacher, they have to go to college and take classes that teach them about different subjects like reading, math, science, and social studies. They also learn how to make fun lesson plans and how to help kids who might be struggling with their school work.
Once they finish college, they have to pass special tests to show that they are really good at teaching. If they pass the tests, they become certified teachers! This means they are ready to go out into the world and teach kids in a real classroom.
So when you see your teacher in the classroom, just remember that they worked really hard to become a certified teacher and that they are there to help you learn and grow too!