Continuous variable - a variable representing a numerical-scale, with equal spacing between numeric values; also called a quantitative variable, scale variable, interval variable, and numeric variable.

Ordinal variable - a variable representing discrete categories that can be ordered from low to high (or vice versa); also called rank-ordered variable.

Categorical variable - a variable representing named categories; also called qualitative variable and nominal variable.

For more information, please see StatPrimer, Chapter 1.