This document summarizes key concepts in consumer theory, including: 1) It discusses the cardinal and ordinal approaches to measuring utility, including concepts like total utility, marginal utility, indifference curves, and marginal rate of substitution. 2) It explains the law of diminishing marginal utility and shows how marginal utility, total utility, and average utility are related through tables and diagrams. 3) It covers the assumptions and features of indifference curves like convexity and how indifference curves illustrate different satisfaction levels. 4) The budget line and consumer equilibrium are defined, with consumer equilibrium occurring where the budget line is tangent to the highest possible indifference curve.