The most common dogs that have a long-haired coat are the Afghan, Bearded Collie, and Bernese Mountain Dog, to the smaller Shih Tzu, Havanese, Yorkshire Terrier, and Maltese.
No matter the breed or length of the coat, all long-haired dogs need regular coat care. A long coat is more prone to getting tangled or matted than most other coat types, especially in places where the coat moves a lot, e.g. between and behind the legs. In most cases, long-haired dog owners brush their dogs every day to every second day.
Long coats need to be brushed or combed from the skin to the ends of the hair, in some cases, you may need to do each length in sections before you can do the entire length. It is best to try and get rid of tangles and mats as soon as you see them before they get any bigger. Sometimes you will be able to comb them out but if this doesn't work you can work conditioner into it then comb it out. Never try to cut out a mat with scissors as the skin can get pulled into the mat and you may cut your dog's skin.