What's A Salary?

An ad poster on the back of a Metro Transit bus said "Hourly vs. Salary".  I didn't give it any thought until a little 8-year old voice piped in from the back of the car.

Voice: Daddy, what's a "salary"?
Me: It's money a person receives for doing a month's work.
Voice: But, that's an allowance!

I wonder how much work she got done last month... :-)