Domestic Long Hair isn't a breed. It's the label used for a mixed-ancestry cat with a medium to long coat, the fluffy counterpart of the Domestic Short Hair. These cats come from the general cat population, so they appear in every color and pattern, from tabby and calico to solid black and smoke. Some resemble a Maine Coon or Persian without sharing that ancestry.
Because there's no breed standard, size, coat texture and personality vary from cat to cat. Most adults weigh 8 to 15 pounds, and the fur can make them look larger. What they share is a coat that needs regular brushing to prevent mats and hairballs, plus the broad genetic diversity that tends to keep mixed cats healthy. Meeting the cat in front of you tells you far more than the label.