What's the difference between the chisel tip and screwdriver tip for soldering irons?
Screwdriver tips have a similar appearance to a flat-head screwdriver with two flat edges. These tips are ideal for making big solder joints for wire to wire and wire to surface work for larger electrical and electronics projects. Chisel tips are similar but are flat-ground on one side and are used for electronics, general wiring and electrical projects. I know both screwdriver and chisel tips come in a variety of sizes too. Here are two images I found of each tip to give you an idea too. They are a bit more detailed than the ones you posted.

Chisel
Screwdriver

Hope that helps!