Stay is the opposite of Come. Instead of Fido coming to you, you come to Fido. It means to remain where you are until you come to him and release him. For the dog in the picture, it means stay on that stump. Therefore, we don't call our dog from a stay.
"Stay" for safety
Stay is used when we need our dog to stay in one place until we come to them. Here are some real-life uses.
1) You come home with an armload of groceries To keep your dog from bolting out the open door, or from tripping you up by getting under your feet, ask them to Stay where they are.
2) Your dog gets away and crosses a street. You don't want to tell them to "Come" because they will need to cross the street again and may not get lucky this time. If you say nothing, they will probably keep running away. Tell them to Stay, while you cross the street and come put a leash on them.
3) Your dog is injured or recently had surgery and not supposed to jump on/off furniture. You're chilling with your dog on the couch and want to get a drink from the kitchen. If you say nothing, your dog will jump off the couch and follow you to the kitchen. Tell them to Stay while you go get the drink and come back to sit with them.
Why return to your dog?
We recommend returning to your dog to release them from the Stay and not calling them to you because it makes the exercise safer. If your dog gets used to being called off a Stay, they will begin to anticipate the release and jump the gun. No big deal if they are safe inside your home, but it can be a huge deal if they are loose and you're trying to reach them to put a leash on. Dogs should be football players because they are great at juking the defense. You are so close that you can touch them and think you've got them, and they suddenly jerk to the side and are gone again. If the muscle memory of Stay meaning don't move until you come to them is solid, you're more likely to be able to retrieve your dog in an emergency situation.