An employer match is a contribution your company makes to your 401(k), sized according to what you put in yourself. Common formulas: 100% of the first 3% of pay, 50% of the first 6%, or 50% of the first 6% plus a small automatic contribution. The formula is in your plan documents, and it is the single highest guaranteed return available to most people.
On a $100,000 salary with a 50% match on the first 6%, contributing 6% ($6,000) earns a $3,000 match. That is an immediate 50% return before the money is even invested. Contributing only 3% earns $1,500 and leaves $1,500 unclaimed every year.
Matches often vest on a schedule. Immediate vesting means the match is yours the day it lands. A three-year cliff means leaving before three years forfeits all of it. Graded vesting releases a percentage each year. Your own contributions are always fully yours.
One trap is timing. If you contribute a high percentage early in the year and hit the $24,500 limit (2026) in September, some plans stop matching for the remaining months because there is nothing to match. Plans with a true-up fix this at year end; plans without one do not. Spreading contributions evenly avoids the problem.
The common mistake is skipping the match to pay down low-interest debt or because retirement feels far away. Almost no debt costs more than a 50% or 100% instant return.