Certification is like getting a special sticker that says you are good at something. For example, if you get a sticker that says you know how to ride a bike, people will trust you and think you're a good bike rider.
Certification can be important for lots of things like jobs or businesses. If you have a sticker that says you are certified to do a job, like fixing cars or cooking food, people will trust you to do it well.
To get certified, you have to show someone that you know how to do the thing really well. They will ask you questions, watch you do the thing, or test you to make sure you are good at it. Once they are sure you know how to do it, they will give you the special sticker that says you are certified.