CRUD is short for four basic ways to work with saved information: create it, read or view it, update it, and delete it.
For example, in a contact list you can add a new person, open their details, change their phone number, or remove the entry. Those are the four CRUD actions.
Developers use this word when talking about screens, services, or databases that manage information. It describes what actions are possible, not whether a particular person is allowed to perform them.