A polar orbit satellite travels pole-to-pole. For a sun-synchronous orbit, it passes over any given point on Earth’s surface at the same local solar time.
Object-based Image Analysis (OBIA) segments an image by grouping pixels together into vector objects. Using these objects, you classify as land cover types.
NDVI quantifies vegetation with the difference between near-infrared (which is reflected by vegetation) and red light (which is absorbed by vegetation).
While Geographic Information Systems answers “what” and “where”, Geographic Information Science (GIScience) is concerned with the “how” and its development.