Answer
A naive forecast simply uses the most recent actual (or last season's actual) as the forecast for the next period. It's a simple baseline/benchmark against which more sophisticated methods are judged; if a complex model can't beat the naive forecast, it isn't adding value. It suits very stable series.
Next month's forecast = this month's actual.Real-world example The team benchmarks its forecasting model against a naive last-value forecast to prove its worth.