These are located on the toolbar at the top of the screen. Initially they will be "grayed out" (disabled) until you draw and/or select shapes.
Copies selected shapes to the clipboard. Keyboard shortcut Control: + C
Pastes the contents of the clipboard into the drawing area. Keyboard shortcut: Control + V
Copies selected shapes to the clipboard and then removes them from the drawing area. Keyboard shortcut: Control + X
Re-do the last operation. Keyboard shortcut: Control + R
Undo the last operation. Keyboard shortcut: Control + Z
Browser variations
The copy and paste button will work on all browsers and tablets as these use the programs internal clipboard, but the short cuts won't work in Firefox or MacOS.
Pasting external images
If you copy an image from somewhere on the web (e.g. Google images) you can paste it into the drawing area by using Control + V not by by using the copy and paste buttons. This is because the image is copied to the system clipboard and for security reason browser will only allow access to the system clipboard for pasting by using a Control + V key combination.
This works In Edge, Chrome, Firefox, and Opera browser. It will work in MacOS, but here pressing Control + V again will paste the same image.