I have been asked for a clarification of the "Local Rule" for a lost ball or a ball hit out of bounds. Starting in 2019, a local rule could be used for casual play that allows a player who has lost a ball or hit one out of bounds to drop a ball in the closest fairway with a penalty of TWO strokes.
For example, you drive from the tee on # 9 and the ball hooks towards the trees on the left. You don't know from the tee if it went out or not. You have the option of playing a 'provisional ball' - an option that should be used in competition - adding a penalty of one stroke.
If you have not played a provisional and you get to the area and can't find your ball, the "Local Rule" allows you to go out to the edge of the fairway, drop a ball and take a penalty of TWO strokes. (If you were in competition and you had not played a provisional, your only option is to go back to the tee and hit another ball.)
The penalty of two strokes would be the same as if you had re-teed and hit your third from the tee. In both cases, your next shot is your fourth stroke.
The diagram below may help (or not):
Remember, this does not apply to a ball hit into a penalty area (aka hazard), where you are not allowed to hit a provisional.