a spider is crawling on a wall. first it crawls 1 meter up, then 1 meter to the left , and then 1 meter down. what is its total displacement?

Displacement means the straight distance from the start point to the end point, no matter what route was followed along the way. The spider ends up 1 meter to the left of where he started, so his displacement for the trip is 1 meter. If he returns to the place where he started, then his displacement will be zero.