A money order is basically a check that you don’t have to wait till it clears. When you buy one, the money is due up front, so when it’s received it can be cashed right away.
Since you are in Canada, if you are having someone from the US send one to you, and this would work the other way around as well, insist they use a International Postal Money order. They are green in color, and are accepted by major banking institutions. I’ve heard nightmares of someone out of the country trying to cash one that wasn’t specifically marked ‘international’
Dave
Hope that helps