GIS (Geographic Information Systems) is the discipline of analyzing spatial data. Collect location data (GPS, satellite imagery, survey data), analyze it (find patterns, answer questions), visualize it (create maps). Use tools like ArcGIS, QGIS, or programming libraries (PostGIS, Folium). Applications: environmental planning, urban planning, real estate (find high-value neighborhoods), logistics (route optimization), epidemiology (disease spread), agriculture (yield mapping).