Select the text, file, or item you want to copy
Press Command + C to copy
Move to where you want to paste
Press Command + V to paste
To cut instead of copy, press Command + X
To paste without formatting, press Option + Shift + Command + V
You can also right-click and choose Copy or Paste
You can use the Edit menu in the top bar and select Copy or Paste
To copy and paste with the trackpad, select the item, then use the shortcut keys above