An administrative centre is like a big house where grown-ups work to help make sure everything in their town or city runs smoothly. Just like how you have a teacher and principal at school to help things go smoothly, the grown-ups at an administrative centre help make rules and decisions for the people who live in the town or city.
At the administrative centre, different grown-ups have different jobs. Some have offices where they make important decisions, others help people with questions or problems they have, and some people are in charge of making sure everyone gets paid on time. It's like a big team where everyone has a special job, and together they make sure the town or city is a nice place to live.