There is a continuum but here are the extremes:
Hard conditions = max sun, min water, min nutrients (sometimes min space)
Hard grown = compact stems, firm leaves (sometimes with curling or other signs of dehydration, often with stress colors), slower growth. Glaucous plants often more glaucous, spiny plants often more spiny.
Soft conditions = filtered light, regular water, regular nutrients (or rich soil)
Soft grown = longer distance between leaves along the stem (or between successive areoles if it's a cactus), weaker stems, leaves greener and often droopy or floppy, faster growth, extreme senstivity to full sun if not gradually acclimatized
Your typical succulent for sale in a big box store is grown soft (a time advantage for growers in getting plants to market). Very few sale plants are grown hard. The economics make this a losing proposition unless your explicit goal is to produce plants that can tolerate harsh conditions right out of the gate. Your typical indoor plant (especially in latitudes above the subtropics) is grown soft unless it gets the absolute maximum amount of light. Your typical outdoor plant in full sun (reminder this means more than half a day of direct outdoor sun) is growing hard unless maybe it gets some kind of special pampering with water and nutrients, and only then in some cases. Light dominates this continuum but water and nutrients play a role, especially toward the extremes.
The hardest conditions are the harshest and the closest to the way things are in habitat for xeric plants. The softest conditions are a product of human care, generally too much protection and pampering, and soft-grown plants often look very much unlike plants in habitat.
