What kind of reaction is acetic acid plus potassium hydroxide?

neutralisation. of Acid + Alkali = Salt + water.

Ethanoic(Acetic) Acid + potassium hydroxide = potassium ethanoate(acetate) + water.

CH3COOH + KOH = CH3COO^(-)K^(+) + H2O

NB Acetic Acid is the old , everyday name for Ethanoic Acid.