Okay kiddo, so an "adjudicator" is someone who is like a judge. They decide if something is fair or right, kind of like a grown-up who decides who gets the last slice of cake.
But an adjudicator usually works for something called a "tribunal." A tribunal is basically a special group of people who make decisions on things that are important, like if someone is allowed to stay in a country or if someone should get money for something. The adjudicator is one of those people in the group who helps make the final decision.
So think of it like this: the adjudicator is like a grown-up who helps decide important things in a special club called a tribunal. And just like a judge, they have to really think hard about what is right and fair before making their decision.