What were the goals of president roosevelt's "fireside chats"? how did he achieve his goals?

Media coverage gives voters an impression of the candidates.

Because much of media coverage comes in very brief news segments and even short "sound bites," it tends to provide an impression of the candidates, without necessarily providing in-depth presentation and analysis of their views. This varies, of course, depending on which "media" you have in mind with the question. Committed news organizations which employ highly skilled journalists will do deeper pieces on candidates and their views or policies -- see, for instance, articles in The New York Times or Washington Post or The Atlantic.

There are many new forms of media--such as social media websites and politically-aligned cable networks--where people can go to get biased perspectives and be told how to vote or not to vote. But the most respected media outets strive to present a full picture and cover all candidates. Still, because most voters will watch or read only portions of news media coverage, the best answer is that media tends to give voters an impression of candidates -- which sometimes is less complete than the full picture.