What is the difference between topographic maps and isochron maps?

a topographic map is a type of map characterized by large-scale detail and quantitative representation of relief features, usually using contour lines, but historically using a variety of methods.

An isochrone map in geography and urban planning is a map that depicts the area accessible from a point within a certain time threshold. An isochrone is defined as "a line drawn on a map connecting points at which something occurs or arrives at the same time".