Ok kiddo, so you know how when we go to church, we sometimes sing songs, and the priest talks to us and we say prayers, right?
Well, a long time ago, people wrote down all those prayers, songs, and things that the priest says in a special book, called a prayer book or a liturgy.
Now, sometimes church leaders decide that they want to make some changes or update the prayers and songs in the book, to make them easier to understand or to reflect what people are feeling or thinking about.
That's what happened with the Book of Alternative Services - it's a special prayer book used in some churches in Canada that has different prayers and songs than the old book.
It's still a book that helps people worship with the priest, but it has some new and different things in it to help people feel more connected to God.