If you want wild-caught salmon, you want Pacific salmon. That's not because wild-caught Atlantic salmon wouldn't be fabulous if we could get it, but the Atlantic salmon sold commercially are all farm-raised.
The Pacific Ocean is home to six types of salmon, and U.S. and Canadian boats fish five of them: King, Sockeye, Silver, Pink, and Chum. To confuse matters, each of these has at least one other name as well as their Latin name, as noted below. They are listed by the most common names you'll likely see at markets.
Oh, and that Copper River salmon you've heard so much about? It's not its own species; it can be king, sockeye, or coho.
Chinook Salmon/King Salmon
Chinook salmon (Oncorhynchus tschawytscha), also known as King salmon, is considered by many to be the best-tasting of the salmon bunch. They have a high-fat content and corresponding rich flesh that ranges from white to a deep red color.
Coho Salmon/Silver Salmon
Coho salmon (Oncorhynchus kisutch) are sometimes called silver salmon or "silvers" because of their especially silver skin. They have bright red flesh and a slightly more delicate texture than Chinook salmon but a similar flavor.
Pink Salmon/Humpies/Humpback Salmon
Pink salmon (Oncorhynchus gorbusha) are the most common Pacific salmon. They have very light colored, flavored flesh and low-fat content. Pink salmon are often canned but also sold fresh, frozen, and smoked. They are sometimes called "humpies" or humpback salmon because of the distinctive hump they develop on their back when they spawn.
Red Salmon/Sockeye Salmon
Sockeye (Oncorhynchus nerka) salmon are noted for their bright red-orange flesh and deep rich flavor. They are known as "reds" both for their dark flesh color and because they turn deep red (from the bright silver pictured here, which is how you'll see them at markets since the commercial catch is caught at sea) as they move upstream to spawn.
Salmo Salar/Atlantic Salmon
While the Pacific is home to several species of salmon, the Atlantic has but the one, the species Salmo salar, commonly known simply as Atlantic salmon. All commercially available Atlantic salmon is farmed. While farmed salmon has a bad reputation in terms of sustainability, salmon farming techniques have made great strides towards greater sustainability, so it's worth looking into the specific source if sustainability is important to you.
Silverbrite Salmon/Chum Salmon/Keta Salmon/Dog Salmon
Chum (Oncorhynchus keta) is also called dog salmon for its dog-like teeth. Keta comes from its species name and is a way to get away from the negative association chum sometimes has. Keta is a smaller fish—averaging about 8 pounds—with pale to medium-colored flesh and a lower fat content than other salmon. Chum is usually canned or sold frozen to foreign markets.