A practicing certificate is like a special permission slip for grown-ups who want to do a certain job that needs special training. It's like if you want to be a superhero, you have to first learn how to save people and then get a special certificate that says you can be a superhero.
For example, if you want to be a doctor or a lawyer or a teacher, you need to first go to school to learn all the important things you need to know. Once you finish school and pass some important tests, you get your practicing certificate. This certificate tells everyone that you are qualified to do the job you trained for and that you promise to do your best to help people.
And just like superheroes need to keep training and learning new things to stay good at their job, people with practicing certificates also have to keep learning and practicing to make sure they keep their special powers and skills. This helps them keep getting better and better at their jobs so they can help more people.