What will collar help you with?
- to walk the dog along without a leash and reliable calling or stopping dog (commands "Stop", "To me", "Stay")
- to interrupt undesirable activities of your dog ("yuck", "must not")
- unlearning bad habits like taking food off the table, jumping at people, pawing, undesirable barking etc..
- to precise your training - the dog can be trained as accurately and reliably as dog was on a leash (hundreds of meters long!) with the removal of undesirable dependence on the leash which the dogs recognize very well and adapt their behavior to it.