Sometimes you open a GIS project with roads, districts, aerial photos, elevation models, and places displayed at the same time. Even though they are shown on one map, they do not all store data in the same way. Some are vector, some are raster. Knowing which is which will help you select the right tool, understand attributes, and not try to run a raster-only tool on a vector layer.
Vector data is made of distinct geographic features defined by coordinates and geometry. Points are used for a bus stop, a sensor, or an address. Lines are used for a road, stream, or path. Polygons are used for a park, a lake, a building, or an administrative boundary. Each feature typically has an associated attribute table entry. A road may display its name and type if you select it; a district polygon may display its population and area. Being able to link a geometric shape with a table record is a reliable indicator of a vector layer.
Raster data is stored as a regular grid of cells where each cell holds a value associated with its location. In an aerial photo, the value determines what color is displayed. In an elevation model, the value is height. Rasters also store things like temperature, precipitation, land cover, or distance. Zoom in close enough, and you can see pixels. This tells you the source data was stored in a grid. Rasters are good at displaying gradual changes over an area, but they do not provide individual features for selection.
Try loading a vector layer and a raster layer into a desktop GIS program. Open the attribute table for each one. For the vector layer, you should see rows connected to specific features. For a raster, you will likely work with cell values, band information, or layer properties instead of a traditional feature table. Use the identify tool on both layers. Selecting a vector feature should bring up its fields and attribute values. Selecting the raster should bring up the value of the cell under your cursor. This simple test highlights how vector and raster data differ in their underlying storage.
File extensions can help identify data types, but you should not rely on them exclusively. GeoJSON, GeoPackage, and Shapefile formats typically contain vector features. TIFF files and digital elevation models typically contain raster data. A GeoPackage, however, can contain multiple types of spatial data, so you should review the layer properties rather than relying on the file extension. You should also check the coordinate reference system, the extent, and metadata. A layer that seems to appear in the wrong location is not necessarily a raster; it could just have incorrect or missing projection information.
This distinction matters most when you are selecting the appropriate tool in a GIS. Buffering a road, selecting parcels, or performing an attribute join are operations that generally require vector data. Changing the brightness of a photo, classifying an elevation layer, or extracting values along a transect generally require raster data. Sometimes you need to use both together. For example, you may display a vector road layer over a raster basemap, or use a polygon to crop an elevation layer. Before executing any operation, double check the data type, the geometry, the coordinate reference system, and the expected result. A quick mental check is whether the layer contains discrete features or a continuous grid of cells. The answer to that question will guide you to the correct tool.
