Any HTML tag (field): you can enter any tag that you want to remove in a comma-separated list. IMPORTANT: if you choose a tag that has child elements, those child elements will be removed along with the parent.
Empty tags checkbox: means empty <div>...</div> rather than empty elements liks <img> etc
Attributes that begin with (field): type the beginning of any range of attributes that you want to match, so entering `aria` will remove all `aria-*` attributes. Enter in this field as a comma-separated list.
Other misc attributes (field): literally any other attribute that you want to remove. Enter in this field as a comma-separated list (type attributes in full).
Celebrate big reductions with 'gusto': basically, it farts. A big, long old raspy fart (but only if you manage to achieve an HTML de-crapulation level of 15% of original markup size).
Remove pointless nested elements button: If you end up with markup with heaps of nested <div>, try this button. It'll strip them out, but will retain any that have an attribute present.