When you say sail, this refers to a verb that you will do when you are about to get into the ocean or the sea aboard a boat. Sailing can take you to different places that may be near or far from where you have started. When you say sale, this can refer to items that are available to be purchased by people.
Sale can also mean that items that used to be priced higher will be priced in a much lower account. Taking advantage of sales will allow you to purchase more items with the budget that you have. Or you can also save up on money and use the money on purchasing other things instead.