The towards operation creates an average of all the selected expressions and replaces each (unlocked) unselected expression with an expression interpolated between it and the average. In geometric terms, the towards operation moves unselected chromosomes towards the average of the selected chromosomes.
Both breed and towards reduce distances in expression space between affected chromosomes; with only these operations available, the search space is gradually narrowed and genetic diversity is reduced, leaving fewer possible choices. The next three operators counteract this phenomenon, increasing genetic diversity.