There are at least two different views of this question.
For pluralists, interest groups help politics and society by giving the people a voice in their government. In this view, people can form interest groups to communicate their opinions to government. The interest groups compete, and the ones with the most support win. In this way, interest groups improve our democracy.
For elitists, interest groups are a way of giving power to the elites. In this view, successful interest groups are formed by those with the most money. These people use their money to get their way through things like lobbying and campaign donations. In this way, organized interest groups help the wealthy elites of society.
Political scientists disagree, then, on the overall impact that interest groups have on politics and society.