Tee time is a reservation that you make for the first shot timing. This reservation is made so that there is a proper flow between games. Moreover, there will be no overlapping between golfers, and people will not have to wait. Most golf courses have tee time reservations, and some of them have made this mandatory. If tee times are not mandatory on any golf course, you can go without booking. However, if the slots are full, then you will need to wait. The same goes for a missed tee time. Only in this case, the course will not refund you the previous tee time fee.