i: Enter insert mode at the cursor position.

Esc: Exit insert mode and return to command mode.

:w: Write the current file to disk.

:q: Quit Vim.

:wq: Write the current file to disk and quit Vim.

dd: Delete the current line.

yy: Yank (copy) the current line.

p: Paste the contents of the yank buffer below the current line.

u: Undo the last change.

Ctrl-r: Redo the last change that was undone.