Bases can be thought of as the chemical opposite of acids. A reaction between an acid and base is called neutralization. Bases and acids are seen as opposites because the effect of an acid is to increase the hydronium ion (H3O+) concentration in water, where as bases reduce this concentration. Bases react with acids to produce salts and water.
A salts positive ion comes from the base and its negative ion comes from the acid. Considering a metal hydroxide as a base the general reaction is:HX(aq) + MOH(aq) → MX(aq) + HOH(l)acid base salt water