What is the name of the abbreviation in SQl queries?

Question

IT terminology

SELECT u.id, u.name, d.name AS d_name
FROM users u
INNER JOIN departments d ON u.d_id = d.id

We have such a request. I missed something and don't understand what these "abbreviations" like ud mean

Answer 1

https://ru.m.wikipedia.org/wiki/Alias_(SQL)