determine your distance traveled and displacement if you walk 100m foward than 35m
Displacement is a vector. This means it also has both magnitude and direction.
e.g. If I walk from point A to point B and back to point A, my displacement would be 0.
http://en.wikipedia.org/wiki/Displacement_%28vector%29
Distance, on the other hand, is a scalar. This means it only has a magnitude value.