Pressure groups, also known as interest groups, play a vital role in a liberal democracy by representing different interests in society and seeking to influence government policy through various methods like lobbying, protests, and public campaigns. While pressure groups can promote pluralism and political participation, some argue they may disproportionately benefit insider groups and business interests or distort the free market and overburden government. The overall impact of pressure groups on democracy is debated, as they can both promote representation but also introduce inequalities and inefficiencies into the political process.