Cyclohexane-1,3-dione is largely enolic in solution, unlike cyclohexanone, whose enol content is negligible. The chief reason is that the enol

In the enol of cyclohexane-1,3-dione the $\mathrm{C}=\mathrm{C}$ is conjugated with the second carbonyl (a vinylogous acid), which stabilises it considerably. The ring geometry holds the hydroxyl and the carbonyl apart, so intramolecular hydrogen bonding is not the cause. The enol is not aromatic. Cyclohexanone has no such conjugation.