Lots of folks spend years learning about Geographic Information Systems technology. But since we promised to keep this brief, we’re going to boil it down to the two basic GIS concepts that you need to know before you can effectively use Geocortex web-based maps. Imagine a tree. How would you keep track of and communicate information about this tree to other people who need to know all about it? You might use a database to keep track of what species it is, how old it is, how tall it is, how healthy it is, and any other attributes (characteristics) that are important. This tree is one record in a database. We call each category (i.e. tree height) a field. Now imagine a grove of trees for which you need to keep track of attributes. Because we are now dealing with more than one tree, it becomes relevant where each tree is so we know what information relates to which tree. We map the location of each tree and identify which attributes belong to which tree. This is the foundation of GIS. A GIS tells us where something is and what it is. Computers are synonymous with GIS, and using a computer we can have hundreds of fields (different attributes) for millions of records (trees). You will be able to examine the attributes of various features as you use a Geocortex web-based map. We can also have other layers of information in our GIS. Our information on trees would constitute one layer of information. We could also have a layer with rivers and a layer with soil types (Figure 4). Any information can be represented as a layer. A map represents the landscape in an artificial way. Vector layers represent features in one of several ways: You might hear people talk about coverages , themes , or shapefiles . All these terms are other names for layers of information. Sometimes a layer of information can be a raster layer, which is a grid that contains information. Rows and rows of pixels make a grid. If you see a photo from above on a web-map, it’s a raster layer. In fact, this is how all digital camera Images are stored. Raster layers don’t have attributes associated with them like vector layers, though they all contain pixel values. That single value might be the color of a roof tile, or it might be a measure of hurricane force for a location, or just about anything else. With individual layers we can conduct analysis between layers or, for example, only display layers that are of interest to us. As you work with Geocortex web-based maps, you will be able to turn different layers on and off as need be. Guess what? You’re done with the theory! With that under your belt, you’re ready to make use of this knowledge. Source.