No, "directory" and "folder" means the same thing here.
I don't know if there's an equivalent for the Mac, but it can be dodgy just to pull out a USB-connected device from a PC if caching isn't disabled for the device, therefore there's a "Safely Remove Hardware" facility.
Anyway, try again. Put the file on the card. Don't unplug immediately. Turn the computer off (I don't know if this is necessary, but just do it anyway unless someone else soon says otherwise). Only then remove the SD card. Put it in your GPS. Turn GPS off and on again. Turn it off and on again again! Attempt to navigate around the map to enough make the screen refresh.