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