[Fn]+[Return] (newer laptops with no Enter key)
** The Enter key (⌤) is different from the Return key (↩) [sic]. On a full Mac keyboard with a right-side numeric keypad, the Enter key is the bottom right corner of the numeric keypad. On older Mac laptops the Enter key is two keys right of the spacebar (i.e. where the right-hand Ctrl key is on a full keyboard).
On current Macs most external keyboards have no numeric keypad and laptops omit the Enter key (⌤). In these contexts either of the latter two shortcuts above can substitute for the Enter key alone. Even with an Enter key available any of the shortcuts may be used.