The layer type defines how each data value will be displayed as a layer. You can use a circle, symbol, line, fill, or fill extrusion. For single points, a symbol or circle are used more frequently. A symbol, such as green cross for a pharmacy, works best when mapping structure and villages/cities. Circles works well when mapping single locations and assessing quantities, where larger quantities have larger circles and smaller quantities have smaller circles, such as the population of a city. Lines work well for geotraces, such as rivers or roads. For polygons, the fill or fill extrusion will work well, such as for data at the region or province level.