This sport began as a way of catching food, and though it has become a sport, and it's one where you eat what you win (except for "catch & release" fishing)! The concept behind fishing is that you attach either bait or a lure to a line attached to a fishing rod, and the fish will eventually (hopefully) think its food, swallow the bait, get hooked, and you get to reel the fish in. Fishing is a relaxing sport (and requires or teaches patience), helps you to unwind, and you can enjoy your natural surroundings--at least until a fish bites.
Fishing can be done from shore, from a pier, or from a boat. The choice will depend on where you are and what kind of fish you are seeking. Once you have picked a sport, you need to select your tackle, either using bait on a hook or a lure. After attaching it to your line, you need to place the bait where you think the fish are. This is called casting, and is done by extending the line a bit and flicking the rod behind you and then forward to use inertia to get the tackle far out into the water. You then reel in the tackle, trying to mimic the movements of the animal your bait is trying to mimic.
Another popular variant on fishing is ice fishing, where you fish through a hole in the ice (often protected by a heated hut or a tent). This usually uses a shorter rod, and is popular in many parts of the country where longer winters create thick ice giving access to deepwater fishing spots to all.
It is considered sportsmanlike practice to keep only those fish you plan to eat. Return the rest for others to catch. Please respect the environment, by not littering, and by not being overly noisy. You should also make sure you comply with provincial regulations regarding fishing seasons, required permits (more on this later)