A CD ladder divides the money you want to invest across several CDs with staggered maturity dates — for example, equal amounts in 1-, 2-, 3-, 4-, and 5-year CDs. As each shorter CD matures, you reinvest it into a new long-term CD at the top of the ladder.
Laddering solves the main trade-off of CDs: longer terms usually pay more, but they lock your money up. With a ladder, a portion of your savings becomes available every year (so you keep liquidity), while most of your money still earns the higher long-term rates. It also smooths out interest-rate risk, since you are continually reinvesting at current rates rather than betting everything on one term. It is a good fit for savers who want predictable, low-risk returns without giving up all access to their cash.