Whether you are new to fishing or a veteran at ripping lips, walking into the local tackle shop to buy a simple spool of fishing line, can be a daunting task, with a plethora of choices.  What are the differences between monofilament, fluorocarbon and braided lines? How about color, diameter, and what test strength?  Here is a quick break down to hopefully make your decision process a bit easier.
The very first question that you must ask yourself is what reel will this line going on, and what are the manufacturer recommendations. Almost every reel you own, has a recommendation stamp that looks similar to this: 6-200, 8-140, 10-120. This simply reads that if you use 6 pound test line, you can fill your reel with 200 yards of line. These numbers are based on monofilament lines, and in most cases braided line and fluorocarbon tend to have a smaller diameter, therefore the capacity will be larger, but it gives us a starting point.

Monofilament
Monofilament, which is commonly referred to as Mono, is the most common used line on the market, if for no other reason than its lower price point. They often come in a large variety of colors that truly have no advantage other than the ability to keep a visual on the line while its in the water. Mono as a general rule, has more water permeability, which means over the course of a day of fishing it will in fact absorb water. This function allows the line to suspend in the upper water column and will sink at a much slower pace than other lines. This function makes Mono a great choice for for fishing top water baits such as buzzbaits and frogs, while being a poor choice for those who are fishing light tackle such as wacky worms and crankbaits.
Monofilament also has more elasticity than other models of line, which gives it a unique advantage to taking on more aggressive strikes. The permeability does however weaken the line over time, which could turn those forgiving stretches into eventual break offs.

Great for: Top water, bobber fishing Adequate for: Spinner baits and surface depth crank baits Avoid: finesse fishing, Natural sinking baits; wacky worms, live minnows, etc , deep running crankbaits

Fluorocarbon
Fluorocarbon is the most versatile line on the market, but not without a more expensive price tag. Compared to monofilament, fluorocarbon has limited elasticity, which creates a more sensitive line. It is more abrasive than most mono lines, allowing it to maintain its strength. It is manufactured to be more dense than water, which results in less slack in the line, and creates a line that sinks rather than floats. Fluoro is virtually invisible to fish, which allows you to upgrade in test strength for heavier fish and more abrasion resistance.
All of these positive attributes, of course come with trade offs. Fluorocarbon is not easy to manage. It is stiffer and has better memory than any other line on the market, making spooling line more difficult. It is also imperative to use either the Palomar knot or the Trilene knot, and requires wetting down when cinching. The lack of elasticity in this line fails to absorb shock strength, such as hard hook sets and aggressive head shaking.

Great for: finesse fishing, natural sinking baits, deep running crankbaits Adequate for: spinner baits, bobber fishing Avoid: top water, surface depth crank baits

Braid
Braided line, or commonly known as super-line, tends to be the best combination of both worlds. Its abrasion resistance, has a small diameter, virtual no memory, and impeccable sensitivity. Unlike mono, where the line sinks extremely slow, braided line does not sink at all, it simply floats, making it a great option for top water lures. It has amazing strength, which is ideal for fishing high vegetation like grass mats and lily pads.
Braid line however is high visibility, making it difficult to use on spooky fish. It has no flexibility, or stretch, leaving you needing more strike absorption on aggressive hits, and knot tying can become a troublesome problem as well.

Great for: high vegetation, top water Adequate for: bobber fishing, spinner baits Avoid: finesse fishing, natural sinking baits, deep running crankbaits.

Monofilament, fluorocarbon, and braid and are the three basic choices of line, however manufactures are constantly creating and marketing hybrid lines that give you the strength of one, but the low memory of the other. I encourage you to try all three, figure out what works best for you in your situation, and begin to experiment with new innovative lines. Often anglers use one line, such as braided line, and supplement the flexibility of a mono as a leader, which would give the stretch and lower visibility needed, but at the same time the ability to fish heavy cover. Mix and match, play around with it, and have fun next time you are on the water.