Sodium fluoride (NaF) is a salt. Although NaF is neither an acid nor a base, this salt forms when hydrofluoric acid reacts with sodium hydroxide. The overall reaction is HF + NaOH --> NaF + H2O
This general type of reaction is called a neutralization reaction: acid + base --> salt + water. Protons from the acid bind to or neutralize hydroxide ions from the base to form water. Meanwhile, the metal component of the base, in this case sodium, binds to the nonmetal component of the acid (fluoride ions) to form a salt (sodium fluoride). A more familiar example of this reaction is HCl neutralizing NaOH to form water and sodium chloride, or table salt.