Minimum-Variance Frontier: The set of all risky portfolios having minimum risk (standard deviation of returns) for a given level of expected return. The horizontal axis is the standard deviation of returns, and the vertical axis is the expected return. The risk-free asset is not included in the portfolios considered for the minimum-variance frontier. The portfolio furthest to the left on the minimum-variance frontier is called the global minimum-variance portfolio, and any portfolio on the minimum-variance frontier is called an optimal portfolio.
Efficient Frontier: The portion of the minimum variance frontier that lies above (and to the right of) the global minimum-variance portfolio: the upper half of the minimum-variance frontier. This is the set of all risky portfolios having maximum return for a given level of risk (standard deviation of returns). The horizontal axis is standard deviation of returns, and the vertical axis is expected return. Any portfolio on the efficient frontier is called an efficient portfolio. All efficient portfolios are optimal, but not all optimal portfolios are efficient.
CAL: A line (technically, if you’re a geometer, a ray) running from the risk-free asset through a given (risky) asset (a single stock, a portfolio, whatever) and on to infinity. The horizontal axis is the standard deviation of returns, and the vertical axis is the expected return. The slope of the line is the Sharpe ratio of the given asset.
CML: The CAL with the largest Sharpe ratio. This line is tangent to the efficient frontier, and the tangency point is called the market portfolio. Thus, the slope of the CML is the Sharpe ratio of the market portfolio. The horizontal axis is the standard deviation of returns, and the vertical axis is the expected return.
SML: The line running from the risk-free asset through the market portfolio and on to infinity. The horizontal axis is the beta of the portfolio, and the vertical axis is the expected return. The slope of the SML is the market risk premium: the expected return of the market portfolio minus the risk-free rate.