Basics of Maps
Vector vs Raster, Projections, Attributes
There are two types of electronic maps: vector and raster. Vector maps are made up of points, lines, and polygons (polygons are areas made up of points and lines). Raster maps are made of pixels/tiny squares. Vector maps have their features positioned mathematically meaning that their position will be perfectly accurate. This means that no matter how far you zoom in, the data will not be distorted, and it provides better data for very precise measurements. This is unlike raster which is based on dividing up the map into tiny squares, meaning the accuracy of measurements depends on the size of the squares. Smaller squares equals more accuracy.
A projection is the way in which we take the 3D sphere of Earth and put it onto a flat plane such as a computer screen or paper map. No matter which way we do it, we will lose accuracy in every part of the map, but it is best to sacrifice more accuracy in the area you will not be focusing on. Basically you can choose to preserve one of the three following items perfectly: Distance, Shape, Size. Whichever you choose, you will lose some accuracy in the other two. This isn't a big deal and is nothing you will have to worry about (unless projections of the map and the data don't match).
Attributes are certain features that are attached to items you have on the map. Say you have a map of counties in Illinois (A state in the USA). If you open the "attribute table" associated with this map, (by right-clicking on the map in the "contents" section and selecting attribute table) you may see that the table has other information attached to each county, for example population, location of county seat, or area of the county. These are the "attributes" that come with the items (the counties) that are on your map. You can add, edit, or delete attributes as you please but if there is an attribute for one item there should be the same type of attribute for all of them.
It is with these attributes that you can make more informational maps, because the attributes are usually the data that needs to be mapped. Say the counties have an attribute of population: you can then symbolize each county with a different color based on the population. The higher the population, the darker the color or whatever you choose. Attributes can also be combined into a new attribute, such as dividing population over area of each county to get population density as your new attribute.