Dolly Varden is always capitalized as it was named for a character in the Charles Dickens book Barnaby Rudge. Though often referred to as a trout, it is actually a char. A quick way to distinguish between trout and char is the size of their scales. The skin of a char is much smoother than a trout as they have larger scales.
Other char include: arctic char, brook trout, lake trout, and bull trout. Bull trout used to be called Dolly Varden, but are now a separate species. Sometimes the areas of Dolly Varden and bull trout overlap. One river which has both is the Taku.
There is two distinct populations of Dolly Varden. The northern Dolly Varden exists in watersheds that drain to the Arctic Ocean, while waters containing the southern Dolly Varden flow to the Pacific.
Dolly Varden spawn in the fall, and can successfully spawn in lakes which have sufficient water flow from springs.