Steelhead are the anadromous (migrating) version of rainbow trout. Rainbow trout are the "land locked" version, and remain in freshwater throughout their life.
Chum, also called "dog salmon," are the second largest of the Pacific Salmon. They are usually found in watersheds closer to the salt water, and not in waterways far inland.
Chinook, also called "king" or "black mouth," are the largest of the Pacific Salmon. They are often found spawning in rivers or larger streams, and are usually one of the earlier salmon species to spawn in the fall.