Everything in studio lighting descends from one decision: where the key light goes. Placed roughly 45 degrees to the side and above the subject, it models a face the way window light does; moved further to the side it produces split lighting with one half in shadow; placed directly in front and high, it gives the flat, shadowless look of classic glamour lighting. The fill light is then added only to control how deep those shadows go — a 2:1 ratio reads gentle, 8:1 reads theatrical.
Hardness of light is governed by the apparent size of the source relative to the subject, not by the modifier's name. A small softbox far away behaves like a hard light; a bare bulb bounced off a nearby wall behaves like a soft one. Colour is the third variable: studio strobes are balanced near 5500 K to match daylight, and mixing them with tungsten or fluorescent room light without correction gels produces colour casts that are tedious to fix later. Metering each light separately, rather than trusting the camera's screen, is the habit that separates controlled results from lucky ones.