my god. i can never get the crop button to work. i always end up with a tiny square of black. thats about 2 pixels wide, and 2 pizels long. YAY. basically! i suck at photoshop, so i don't use it. i don't understand tutorials either. sorry! this was such a pointless reply! you probably tought someone was helping you...but it's just me...not helping.. i'll shuttup now
If you crop an image, it basically means that you're cutting off a part of the image and making the picture smaller by using the crop tool. And duplicating means just like it says: it duplicates the layer. You can do this by either right clicking the layer and hitting the "duplicate layer" option on the drop-down menu, or pressing ctrl + j on your keyboard. Hope that helped! ETA: Are you sure you're not just clicking the picture once? Make sure you drag the tool to your desired size. If that doesn't work, I'm not sure what's wrong.