A few types of molecules get sensed by receptors on the tongue. Protons coming off of acids ping receptors for "sour." Sugars get received as "sweet." Bitter, salty, and the proteinaceous flavor umami all set off their own neural cascades.
dcterms:bibliographicCitation
2018 May 16, Adam Rogers, “The Fundamental Nihilism of Yanny vs. Laurel”, in Wired: