Run-rate is current performance annualized: taking a recent period — a strong month or quarter — and extrapolating it across a full year, such as multiplying a month's revenue by twelve. It is used to express what current momentum implies for annual performance.
The risk in run-rate is presenting a favorable recent period as steady state. Annualizing a peak ignores seasonality, one-off events, and the durability of the recent result, and it can flatter figures that will not repeat. A run-rate is a useful shorthand only when the base period is genuinely representative of ongoing performance.