The symbology available for a layer depends on the type of layer, and on whether the geographic data provided to the layer consists of points (X/Y values in either decimal degrees or other units) or polygons (geographic areas).
When the geographic data consists of points, each point is represented by a marker on the map. Each marker can be drawn using a standard shape or an image file. Markers can be assigned a size and can be colored based on several classification schemes, using any metrics.
When the geographic data defines polygons, the areas on the map representing each polygon can be colored based on several classification schemes, using any metrics. It can have an outline that consists of a color, a thickness, and a line style. It can also have a fill style such as solid, diagonal lines (forward or backward) or crosshatch.