Primary key
The column that identifies one row and only one, for ever. It must be present and it must be unique. Usually it's a number or a random id with no meaning, because anything with meaning, like an email address, can change.
An agent asked to model users may reach for the email as the key, which works until someone changes their email and every link to them breaks. It may also pick counting numbers for public URLs, which tells anyone how many orders you have and lets them guess the next one. Say what you want.
Say it to your agent
“Give every table a primary key column called id, generated by the database, with no business meaning. Don't use email as a key. Use a random public id in URLs, so nobody can count our orders or guess the next one.”