The main differences are usually subtle, and they’re hard to judge from tiny thumbnails. What changes most is how diffuse and how large the light source appears relative to the subject.

As the light becomes larger/more diffused:

• shadows get softer, with smoother transitions from highlight to shadow
• shadows fill in more, so overall contrast decreases
• the light “wraps” around the face more evenly
• skin texture and blemishes are emphasized less
• specular highlights and catchlights become larger and less point-like

With a small, direct source, the light is harder:

• darker shadows
• more abrupt highlight-to-shadow transitions
• stronger contrast
• smaller, brighter specular highlights

So the first example is likely showing harder light, while the others are progressively softer variations. In portraiture, softer light is often preferred because it is more flattering. To really see the differences, view larger images and compare shadow edges, catchlights in the eyes, skin texture, and overall contrast.