Abridgement means taking a very long story and making it shorter. Imagine you have a big book with lots of words and pictures. Abridgement is like taking all the important parts of the story and putting them into a smaller book that is easier for you to read.
Think of it like packing for a vacation. You want to bring all your favorite toys and clothes but you can't carry too many things in your suitcase because it will be too heavy. So, you have to choose only the most important things and leave the rest behind. Abridgement is like packing your favorite things into a smaller suitcase so you can still have fun, but it won't be too heavy to carry.
Sometimes people do this with really big, important books like “Encyclopedia” to make it easier for people to read and understand. This way, people who don't have a lot of time won't have to read the whole book and can still get the most important information. This is called an abridged version of the book. It's like reading the most important parts of the story without having to read everything.