This is an acronym for Create, Read, Update, and Delete.
Each piece of data that you want to store is referred to as a record. It’s a recording of the data. You’ll need to make it exist somehow. That might be via an add button, a set of form fields, or even something automated. Either way, the record is created. This also implies that it’s saved to the database. You’ll also likely want to look at it again someday. This would be reading the record (reading the database, and probably displaying the records). You might want to change your username or address. This would be updating the record. And sometimes you don’t want to keep the record anymore. Maybe you want to delete your Facebook or maybe you checked that todo item off your list. That’s deleting it!
CRUD! It’s not just that dry mud on your shoes. It’s a silly term to describe how we interact with databases.