Most notably, the central bank may try to convince markets that it would keep interest rates low, even if this would imply inflation well above its previous objective, at least temporarily. The promise of higher future inflation, if credible, induces private agents to substitute future for current consumption, hence providing additional stimulus today.
A variability range of plus/minus one percentage point around this benchmark was added later, an addition which should not be interpreted as a target but as an acknowledgment of uncertainty stemming from the highly volatile nature of some components of the price index.