When you're moving at $5$ m/s for $1$ second, you have traveled $5$ m.
When you're moving at $5$ m/s (initial velocity) and you accelerate $2$ m/s for $1$ second, you have traveled $5$ m + $1$ m (distance traveled because of acceleration).
But does this hold true in real life? If I was to test this out, would the distance traveled because of acceleration equal $1$ m?