Here's a breakdown:

* Natural selection is a key mechanism of evolution.

* Favorable traits are those that increase an organism's chances of survival and reproduction in a particular environment.

* Unfavorable traits decrease an organism's chances of survival and reproduction.

Through natural selection, individuals with favorable traits are more likely to survive, reproduce, and pass those traits on to their offspring. This leads to a gradual increase in the frequency of favorable traits in the population over time, while unfavorable traits become less common.