An application or loan is reported if it falls into one or more of the following three categories: home purchase loan, home improvement loan, or refinancing.
1.A home purchase loan is any loan secured by and made for the purpose of purchasing a dwelling.
2.A home improvement loan is: (a) any dwelling-secured loan to be used, at least in part, for repairing, rehabilitating, remodeling, or improving a dwelling (or the real property on which the dwelling is located); or (b) any loan not secured by a lien on a dwelling to be used, at least in part, for one or more of those purposes that is classified as a home improvement loan by the institution and is used, in whole or in part, for repairing, rehabilitating, remodeling, or improving a dwelling (or the real property on which the dwelling is located).
3.A refinancing is any dwelling-secured loan that replaces and satisfies another dwelling-secured loan to the same borrower. For reporting purposes, both the existing obligation and the new obligation must be secured by liens on dwellings.
That is straight from the HMDA Getting It Right Manual.