Also known as a "contingent deferred sales charge or load."
The back-end load is a type of sales charge that is used with mutual funds that have share classes, which in this case are identified as Class-B shares. Class-A shares charge a front-end load, which is taken from an investor's initial investment. Class-C shares are considered to be a type of level-load fund - no front-end and low back-end loads, but the fund's operating expenses are high. In all cases, the load is paid to a financial intermediary, and is not included in a fund's operating expenses.
In essence, funds with share classes carry sales charges (as opposed to no-load funds). The class you choose is what determines how much and when you pay. In employer-sponsored retirement plans, the loads are generally waived.
Investment dictionary. Academic. 2012.