Okay kiddo, let me explain to you what a lectionary is. Have you ever seen a big book in church that the priest or pastor reads from during the service? That book is called the Bible. But sometimes the priest or pastor reads from a smaller book that has different readings in it. That smaller book is called a lectionary.
The lectionary is a special book that has different Bible passages in it that are chosen for each Sunday and special days of the year, like Christmas and Easter. It helps the priest or pastor decide which Bible readings to share with the congregation on a specific day.
The lectionary is used in churches of different Christian denominations all over the world, and it helps us all follow the same plan for reading and studying the Bible together. It's like having a special schedule to follow when we're learning about God and His word.
So in summary, a lectionary is a special book used by churches to choose specific Bible passages for each Sunday and special days of the year. It helps keep us on a schedule for learning about God and His word together.