What does a line in between two individuals represent?

In a pedigree chart, the line which is horizontal shows the parents which mated and produced the children which are represented in the vertical lines below them.

A pedigree chart can be described as a diagram which illustrated the sequence of ancestors of an individual. Often, a pedigree chart is used to look for genetic traits or genetic disorders which might run in the family history. Pedigree charts are important for understanding the probabilities of the offsprings in which a genetic disorder might occur due to family history.