Synopsis
As a secondary skill, fishing occupies its own unique space in World of Warcraft. Although it is essentially a gathering skill akin to skinning, herbalism, or mining, the mechanics of the skill make it almost like a mini-game. Just like the real-life equivalent, to become a master fisherman you'll have to spend considerable time standing next to bodies of water while holding a fishing pole. Catching a fish will be a test of your reaction time, as you have to right-click the bobber immediately after you see it dip into the water indicating you've caught something.
Along with the requisite marine life such as fish, eels, and squid, you also might haul up some odds and ends from time to time - including even valuable items, some of which may only be caught by fishing. The fish you catch can be eaten on their own to regain health, or they can be used in cooking recipes. The cooked fish will often provide useful effects when eaten.
And, like any real-life fisherman will tell you, part of the appeal of fishing is its inherent relaxing nature. Finding a perfect fishing spot, secluded from other players and (hopefully) enemies, while surrounded by beautiful scenery - it's a perfect way to take a break from your adventures in the World of Warcraft!