What does the "2, 3" part of this compound mean? 2,3-dimethylbutane.
2,3 just means that the second and third carbons have a particular substituent (set of atoms) called methyl groups attached.
According to IUPAC nomenclature, the name butane indicates that there are four ("but") carbons in the parent chain (main chain) of the alkane ("ane"), a type of hydrocarbon.
Additionally, 2,3-dimethyl indicates that there are two ("di") methyl groups attached: one on carbon 2 and one on carbon 3.
The main chain has been highlighted, and carbons 2 and 3 are where the two not-highlighted methyl groups are attached.
CHALLENGE: Can you draw the structure of 2,2-dimethylbutane?