"Hard light" comes form a single point source and thus produces sharp or "hard" shadows. On a sunny day, the sun produces very hard light. So does a slide projector or a flashlight. Conversely, "soft light" comes from a large, diffuse source. As a result, shadows are less defined--or perhaps not even visible at all. The fluorescent lights in most any classroom produce soft light. So do the clouds on a cloudy day.