cooking vs simmering

cooking and simmering both are nouns.

Word	Noun	Adjective	Verb	Adverb
cooking	Yes	No	No	No
simmering	Yes	No	No	No

As nouns, simmering is a hyponym of cooking; that is, simmering is a word with a more specific, narrower meaning than cooking:

cooking: the act of preparing something (as food) by the application of heat
simmering: cooking in a liquid that has been brought to a boil

cooking (noun)	simmering (noun)
the act of preparing something (as food) by the application of heat	cooking in a liquid that has been brought to a boil