The lava on the right is shiny and smooth, and it has its own name, like aa a Hawaiian wordpahoehoe. In Iceland, this kind of lava is called helluhraun. Smooth is a relative termsome forms of pahoehoe can have a surface as wrinkled as an elephant's trunk, but not at all jagged like aa.
What makes the exact same lava produce two different textures, pahoehoe and aa, is the difference in the way they have flowed. Fresh basalt lava is almost always smooth, liquid pahoehoe, but as it cools and crystallizes it turns stickythat is, more viscous. At some point the surface can't stretch quickly enough to keep up with the movement of the flow's interior, and it breaks and shreds like the crust of a loaf of bread. This can happen simply from the lava growing cooler, or it can occur as the flow spills down a steep place making it stretch faster.
For photos of related rocks, see the volcanic rocks gallery.