This reagent is one of my favorite ones for replacing an alcohol with an iodine.
Eric Kool's lab has made good use of it to iodinate the 5'-OH after automated synthesis of a DNA strand.
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Normally, iodine just makes one bond, as you'd expect from a halogen. Some compounds, though, force it into lively higher oxidation states (hopefully without the tendency to explode, as some highly oxidized iodine reagents worryingly exhibit).
Potassium iodide isn't much of a structure:
It's a source of iodide. Thyroid hormones contain iodine; the source of this is dietary iodide.