What's that metal wounded filament sponge looking thing and what is it used for?
Cleaning a soldering iron tip

It usually sits in a metal dish, and you push the soldering iron into it and wiggle it around to clean the tip.  It's an alternative to a damp sponge, which always used to be built into soldering iron stands.

You should clean the tip just before use if it has darkened. Then put it back in the stand with the solder on after making a joint, and clean again if necessary before the next joint.  That way you leave a drop of solder on the tip when it is in the stand, which slows down oxidation.