Okay kiddo, imagine you are at a church service and everyone is singing together. Sometimes, the words they sing are written in a special way that tells a story or teaches something important about God. This way of writing is called a canon in hymnography.
A canon is like a puzzle that you have to put together. It has different parts, called voices, that all sing the same melody but start at different times. When you put all the voices together, they create a beautiful harmony that sounds like one big, happy song.
The words in a canon often have a pattern that repeats over and over. For example, they could start with a line like "Glory to the Father" and then add new lines to that same melody, like "Glory to the Son" and "Glory to the Holy Spirit". This way, you can sing the same melody but say different things about the different parts of God.
So, canons are a special way of writing hymns that use repeating patterns and different voices to create harmony and teach important lessons about God. Pretty cool, huh?