For brevity (and because it's late and I need to get to bed) I will lump replies to a couple of comments together.

To KenK regarding datums: To be strictly correct, newer USGS topos use NAD83. However, functionally, NAD83 = WGS84. My understanding is that the difference between WGS84 and NAD83 is less than 1 meter (usuually much less than 1 meter). Even the potential difference between NAD27 and WGS84/NAD83 is not huge in most cases. In my area (Southcentral Alaska) it amounts to ~115 meters. Some areas may be more than that, but usually little more than a couple of hundred meters. Back in the dark ages before GPS, we were often thrilled to fix our position to within 200 meters.

To hikermore regarding magnetic declination diagrams:This is correct, assuming one is orienting the map to terrain (which is what one does ~99% of the time). However, the comment was in reference to using the compass to orient the map. The implication (at least to me) of the comment I referenced was that someone could just align magnetic north from the compass parallell with the magnetic north line on the little diagram, to orient the map. This can get you into trouble. (This would work on a compass rose on a nautical chart, since there the angle of the diagram is correct. However, on a USGS topo map, the angle on the diagram is schematic only.)

To various people who have commented on the amount of magnetic declination, and how fast it changes:
This really depends on where you are. For example in Chicago, declination is only 3 deg 28 min W, and is only changing by 5 min W per year. In Chicago you could probably ignore declination and get away with it for many purposes. However, where I live in Anchorage it is currently 18 deg 23 min E, and is changing by 18 min W per year. That means it changes by almost one degree every 3 years. Not a good idea to ignore it here.

To the original poster JeanetteIsabelle:
Don't let all these technical details scare you off. It really isn't that hard to aquire a basic working knowledge of navigation. Take it one step at a time. Use the old 'walk before you run' approach. Don't worry about a compass or GPS at first. Get your hands on a basic book, any of the several that have been recommended should be fine. Get a topo map of some area that you know well or that you plan to visit. Just start walking around, map in hand. You soon will develop a feel for how things are portrayed on the map vs the ground you are walking on. Ideally, find a place where you can get up high a bit and get a view of the surrounding area. The top of a hill, or even up a few floors on a building will work. Again, just start comparing map to terrain.

Once you have a basic feel for how things are portrayed on a map, then start thinking about learning how to use a compass. Again, just start simple, and work your way into more challenging situations. Here is where the book might be very helpful, or one of the free classes offered by REI or similar places.

Don't even think about getting a GPS until you have a good handle on basic map and compass stuff.

Besides a very useful skill, you will find that navigation can be a lot of fun for its own sake.