command

[HeatherNewton]

sme=((Customer_type='C'));

I have a command like this. What does it mean? I dont know how to google this and what is the key command here...?

[PeterClemmensen]

This is called a Boolean Expression. It returns 1 if Customer_type='C' and 0 if not.

You don't need any of the parentheses. Though many programmers like to have a set of parentheses around it to highlight that it is a Boolean Expression. 

[Kurt_Bremser]

It's not a command, it is an assignment statement.

Customer_type='C'

is a comparison, which yields 1 (true) when the condition is met, otherwise 0 (false). The resulting value is stored in variable sme.