Okay kiddo, so imagine you are a Catholic bishop and you live in a far-away place like Africa or Asia. You believe in God and follow the teachings of Jesus, and you want to make sure you are doing everything right.
That's where "ad limina" comes in. It's Latin for "to the threshold" and it means that bishops have to visit the Pope in Rome every once in a while. Imagine it's like going to see the boss at work, but the boss just happens to be the leader of the entire Catholic Church!
During the visit, the bishop gets to talk to the Pope and other important Church leaders. They talk about important things like what the Church should do to help people, how to teach people about God, and any problems that are happening in their part of the world.
The bishop also gets to visit churches and holy places in Rome, which is cool because that's where a lot of important things happened in the early days of the Church.
Overall, going to ad limina is a way for bishops to make sure they are doing their job right and to get advice and help from the Pope and other Church leaders.