Make a selection first—Copy Command+C and Cut Command+X operate on the selected pixels and are disabled without a selection. Copied pixels land on the clipboard as a regular image, so they paste into any app.
Choose Edit > Copy Merged Shift+Command+C to copy the entire canvas as it is composited from all visible layers, including layer opacity and transparency. Copy Merged does not require a selection.
Choose Edit > Paste Command+V. The image arrives as a floating selection you can position before setting it down. Dottie pastes:
Choose Layer > New Layer with Clipboard instead to create a new pixel layer directly from the clipboard's bitmap image, fitted and centred to the canvas—unlike Paste, it lands as a regular layer rather than a floating selection.
Choose Edit > Copy Cursor Position Control+Option+Command+C to copy the hovered pixel’s coordinates as “x,y” text—useful when writing scripts or documenting sprite offsets.