They're quick cheap sketches used to practice.

i see

An iron artist is where an artist will take 100 commissions at a flat rate, usually sketches or flat colors something they can pump out quick. The goal is to improve your style or work on something simple. the goal is usually to finish as many as quickly as possible and unlike normal commissions there isnt usually a "touchup" feature. It's more of a get what you get.

Give a brief description of what you're after
a few character examples (pictures work best)
and possibly a few notes (five or less are best)

the artist asks for a simple list of things like above and then draws as many as he can as fast as he can

well, that's more in depth, i may have to try this sometime when i get more free time