Crud is an acronym that stands for Create, Read, Update, and Delete. It is used to describe operations on data.
Imagine a library with books. To create a book, you would need to get words and put them together in a way that makes sense. That is creating.
To read a book, you would need to look at the words and understand the meaning. That is reading.
To update a book, you would need to change some of the words to new words or add more words. That is updating.
To delete a book, you would have to take all the words away so it cannot be read. That is deleting.
So, crud is a way to talk about all the different things that can happen to data like books.