What is the meaning of '@' symbol in Oracle SQL?

Question

What is the @ symbol mean in oracle?

For example:

select * from question_answer@abcd where id = \'45\'

Answer 1

It refers to a non-local table, the bit behind the @ is the db descriptor.

select * from question_answer@abcd where id = '45'

Means select not from the local question_answer table, but from the table on the db designated as abcd. The keyword to google for is dblink