Enols are alkenes (en) that have a alcohol (ol) function directly attached to the alkene C-atoms. One way of forming enols is by way of tautomerization of enolizable ketones. Acetone is an "enolizable" ketone since it there are hydrogen atoms attached to the C-atoms that are directly connected to the carbonyl C-atom. Migration of one of those enolizable H-atoms to the carbonyl-oxygen atom give the enol tautomer shown.