Answer:
Directed evolution is the laboratory process by which biological entities with desired traits are created through rounds of genetic diversification. It can also be created through library screening or selection and has become one of the most useful tools in basic biology. It's role includes improving the stabilities or biochemical functions of proteins by repeated rounds of mutation and selection.
More simply said, directed evolution is a mimic of the natural evolution cycle in a laboratory setting.
It has indirectly revealed that single amino acid mutations can enhance properties such as catalytic activity or stability and that adaptation can often occur through pathways consisting of beneficial mutations.