Okay kiddo, have you ever seen a litter of puppies or a group of flowers that all looked the same? That's kind of like what wild type means.
When scientists study living things, they often look for how they are similar and how they are different. The "wild type" is kind of like the normal, or "default" way that a living thing looks and acts.
For example, if scientists are studying a type of fruit fly, they might compare all the fruit flies they have to the "wild type" fruit fly. That way, they can see what traits are different or unusual in the other fruit flies they're studying.
Basically, wild type means the normal or most common way that a living thing is supposed to be.