We know that displacement is the length of straight line joining the initial position with the final position. as lisa walks around the block once, she comes back to her initial position here she started from, hence the initial and position of lisa is same. so her displacement is zero.
We know that distance is the length of the actual path followed by object between initial and final position. As lisa walks around the block once, she travels 1 mile. hence the distance traveled by lisa is 1 mile.
displacement : 0
distance : 1 mile