Briefcase - is used to synchronise files between two PCs such as your desktop and a laptop.
Copy - makes a copy of selected text, images, files and holds it in memory
Paste - makes anew copy of selected text, images, files in the current location.
So to copy a file you right click and select Copy. Then goto a new folder and right click and select Paste. A new copy of the file will be made in the new folder. Cut does the same a Copy but removes the original item when its Pasted so it moves the file instead of copying.