Question : How to use alias in MYSQL searches?

I seen some hints that i can use something like alias in searches, like making a select statement becoming A. How is this done?

its from the question http://www.experts-exchange.com/Database/MySQL/Q_23559566.html

Answer : How to use alias in MYSQL searches?

See attached additional clarifications.

explanations.txt (1 KB) (File Type Details) 

Hopefully, more clarification.