USD/CAD fx: What's the difference between Buying USD and Selling CAD? Beginner question here.
I'm Canadian, and my investement account is, by default, in CAD currency.
Recently I wanted by buy a US stock so I had to convert some of my CAD money in USD money.

There would have been other ways, but this led me to use an FX tool. The interface was similar to this:

Action: [ ] Buy [ ] Sell

Currency: [ ] CAD [ ] USD

So basically, in order to do what I wanted to do (convert CAD to USD), I had 2 options:

A) Buy USD

B) Sell CAD

What's the difference between both actions ?
Should be no difference. 

You are either (1) buying USD by selling CAD or (2) selling CAD to buy USD.