I often see people who misuse reinforcement markers. A reinforcement marker can be a clicker, a particular word or sound. An association between the marker and a reward is the first thing that is taught. Once the dog understands that the click, word (many people use "yes") or other sound means a reward; then you can use it to mark correct behaviors. There is a great deal to know about marking behaviors, timing and delivery take patience to master. Using markers is very commonly done wrong; which can leave a dog in a state of confusion.
A reinforcement marker must be understood fully before it can be used correctly. Often owners who have heard about it may give it a try without having any sound knowledge of what they are doing. I have seen trainers, attempt to use and teach it without any real knowledge of what they are doing. When someone misuses a behavior marker; it can cause a great deal of frustration in a dog. You may end up with a situation similar to "the blind leading the blind."
The marker means a reward is coming. The marker has great power because of it's association to the delivery of a reward. Each and every time the marker is used, a reward MUST follow. If the trainer does not deliver a reward when the marker is used; then the marker will have diminished power. It will no longer be a marker in the capacity that it is meant to be.
Like I said, a marker can be anything; a sound, a word or even a flash of light. People who work with deaf dogs often use flashlights as their behavior markers. When a dog is learning a new behavior; the marker speeds things along once the dog has a clear understanding of it. Timing is of the utmost importance and needs to be practiced to get it just right. I use a clicker and the word "yes." If I am out somewhere and Elsa offers me a new behavior; I like to be able to mark it, even if I do not have my clicker on me.
A marker gives you the ability to work away from your dog. You can be clear across the room and still mark a behavior. By creating an association between a desired behavior and reward; we give our dogs very fast information that has pinpoint precision. The dog quickly learns what particular behavior is getting them the reward. They then think about how to do it again and you get a repetition of desired behaviors. Once a behavior is solid and proofed you can then wean off the rewards by variable intervals. You can use time or random delivery to work your way to complete elimination of rewards. BUT, when you are weaning off of a reward; you implement verbal praise. Different words other than your marker word must be used; because if you use your marker word it MUST be followed by a reward.
A marker is not used as a bribe; it is not a reward in itself. It is a marker, in the simplest form. But before the marker can do it's thing; it must be associated to a reward. That reward can be food, a ball, tug toy or anything else that your dog would consider a reward. Never click, say "yes" or use your marker without rewarding it. A behavior must be offered to be marked; once marked a reward MUST follow. If you don't understand about the use of a behavior marker; read up on it and ask a trainer who is well experienced in the use and misuse of a behavior marker.