I have always wanted to be a journalist, which is a person who writes news or other current information to the public.
What is their major function?
Journalists work with general issues or in specific issues. They inform the public about events the public would not know about.
That means they are source of the news we listen to 
Correct. A journalist's work is usually called journalism. It can be written or spoken form.
What more do you know about a journalist?
Most journalists specialize in certain areas that span many topics. For example there are sports journalists.
And?
A reporter is a type of journalist who researches, writes, and reports on information in order to present in sources, conduct interviews, engage in research, and make reports. The information-gathering part of a journalist's job is sometimes called "reporting", in contrast to the production part of the job such as writing articles. Reporters may split their time between working in a newsroom and going out to witness events or interviewing people. Reporters may be assigned a specific beat or area of coverage.
Depending on
Journalist
A journalist is a person who collects, writes, or distributes news or other current information to the public. A journalist's work is called journalism. A journalist can work with general issues or specialize in certain issues. However, most journalists tend to specialize, and by cooperating with other journalists, produce journals that span many topics. For example, a sports journalist covers news within the world of sports, but this journalist may be a part of a newspaper that covers many different topics.
Roles.