As others have said the question has many answers. All lines have their pros and cons, and specific uses as well. A few examples are as follows:
- Braid is really strong in a small diameter, potentially allowing much more line to be put on the reel. Great around wooden snags but rocks can slice through it easily. Usually the most expensive
- Fluorocarbon is just a hair thinner than mono and also is practically invisible in the water. Usually just a bit cheaper than braid.
- Monofilament is the cheapest line but don't let that fool you. It's great around rocks and has the most stretch, which can be a good or bad thing depending upon your intended use.
Here's an article for you, you can also Google search for "choosing the right fishing line" and watch videos/read more articles.
linky It may also be helpful to give us what you're after and where and someone will give some helpful suggestions. I personally use 30lb braid to a 20lb coated braid leader and fish almost exclusively for carp/buffalo. Tight lines!