One of the best ways to present a world to your players is via a map. It makes everything more tangible and gives an easy to look at representation of travel time, geography, population density and many other things. Maps can also help create a certain style of game play or help set the voice of your world. My favorite part of using maps is that they can act as a great obstacle to the characters, or conversely, a great help.
So how can maps help create a style of game play? Well first we can look at the generalities of using a map versus not using a map. Games which do not use a map can not be as tactical, and rely on the players trusting the DM to not be clear and forgiving when it comes to distances, travel routes in combat and all the various combat rules that apply to them. When not in combat, there is a much less tangible feel of distance traveled, as it simply becomes a number of days or miles put in, as opposed to being able to trace a line from point A to point B along the route traveled, seeing the terrain as you do so, and evoking that feeling of "Holy Shit!?!?!? We came that far through that terrain", simply due to the fact that the description of travel will fall away and be forgotten, but the map re-describes the journey each time it is looked at.
Now that was just a general look at maps vs not maps, and it is easy to see how a map can help create a style of game play. I want to mention that while I prefer maps, mapless games are just as valid as mine, they just set a different tone to the game.
Now, to look at three styles of maps I know are used for games such as Pathfinder, at a long distance travel level. These three maps are Point to Point, General Layout and Detailed.
Point to Point maps are the easiest to make, and the least detailed. They have the rough shape of a country/continent/world/etc and have all of the major locations shown on the map. There may be roadways drawn as well, but they are unnecessary for the Point to Point map. Other than the map there is some form of key denoting travel times between places and that is it. The map is basically a teleportation grid. There may be an encounter/encounters during the travel, but there are no routeing decisions, no risk of getting lost and, nothing notable between the points unless the DM mentions it during travel.
General Layout Maps are the kind I have used to create the initial layout of my world. I also use them in area where my Detailed maps are not yet finished. These maps have the key locations of the area, as well as key geographic features and layout of the world. They require little in the way of making past the Point to Point map though, generally just drawing in of mountains, rivers, plains and forests in great broad sweeps. The key difference is in how they are used. With a General Layout map, the party can travel where they want, knowing what the rough terrain is going to be and decide to avoid certain areas to affect travel times, ease of access, ease of pursuit etc. They give more responsibility to the party for their circumstances, good or bad, and help bring the world to life more.
Detailed maps are done at a scale of 20 mile to a side hexes or smaller. They give the positions of everything, as well as much more minute changes in terrain. The hexes I use are one mile to a side, so 2 miles from point to point, or 1.67 miles from face to face. The maps I generate with them are fairly detailed, and I annotate locations as small as hamlets of 2-3 people on them. In an ordinary day of travel my players cover 8 hexes, and I have created a movable halo over the map so they can only see 8 hexes in any direction from their point at any time. This means that the survival skill, as well as knowledge geography plays a larger role in my game when they are in difficult terrain.
These three styles of maps can help create many different voices for a campaign depending on how they are used. Point to Point maps helps create a game where the destination matters. The game could be a tactical string of missions or a nicely woven narrative, or anything in between, but the destination is more important than the journey.
General Layout maps help foster a game where the journey matters. It is not just about where we are going, but how we are getting there, and then leaving there that matters. It helps bring weather into play as getting caught in different terrains makes the same weather affect the party in different ways. The game does slow down a bit however, as the route must be chosen. This leads to more time between other scenes as the players determine the best way to travel through an area.
Detailed maps bring route choice to an entirely new level. They do not slow the game down much more than General Layout maps, they imply take a much longer time to create. They allow terrain choice to become a significant factor in the game, as well as travel route. It also brings the world more to the fore, as there are more details of it for the players to immediately see.
Now, I have just touched on the basics of maps here. There are many more ways to use them than this, and all three styles of maps have there place in creating the voice you want for your adventures. You can even use all three at different levels within the same game. I use the General Layout and Detailed types of maps for overland travel and for the players to plan their journeys with. In cities I use Point to Point maps, as the exact terrain and layout matters less as the excitement is largely at the destinations. However you chose to use maps, makes sure you put some thought into it before hand, as it can greatly help you run your game.