Conation is the component of the mind that has to do with what drives an individual to act and strive. While the other two components of the mind, affect and cognition, have to do with emotions and knowledge respectively, Conation is about exercising one's will.
As an example, let's say you needed to get your math homework done. Cognition has to do with things like whether you understand the concepts needed to solve the math problems assigned to you. Affect has to do with whether you like the subject or not. Let's say that you don't fully understand the lesson, and don't like the subject all that much. But, you know that you need to somehow pass the course in order to graduate, which is your ultimate goal. Conation is what will drive you to make the effort to hit the books and go through the math problems even if you dislike the subject. Conation allows you to exercise your will and act upon your thoughts and emotions.