Political parties exist to advance the agendas of like-minded people. In general, they represent the aggregate consensus of individuals who have joined together under one organizational umbrella to push their preferred policy prescriptions or proposals through legislative processes in the hopes that those prescriptions or proposals will become the law of the land. In most political systems, parties are the most visible manifestation of an ideology, a set of ideas about how government should function and serve the public it represents. In two-party systems, such as the one that has dominated the United States political landscape for many years, the two parties or blocs compete for power, and the prevailing side has the greater opportunity to advance its agenda. In multiparty systems (e.g., Italy, Israel, Germany, and so on), there are often two large parties surrounded by a number of smaller parties. When neither of the larger parties constitutes a majority within a parliamentary system, they both attempt to form coalitions with smaller parties until a majority of seats is achieved. This can actually undermine democratic principles by giving small political parties a disproportionate amount of power. While these smaller parties represent a tiny percentage of an overall electorate, they use their leverage with the larger parties to win concessions on specific issues.
Pressure or lobbying groups are an essential component of a democratic process. They represent the freedom of a citizenry to petition its government for changes each group deems necessary. Pressure groups are like political parties, but they focus on a limited number of issues. Issues like gun control, reproductive rights, immigration, and foreign policy (usually focused on a particular country like Greece, Poland, India, or Israel) are the focus of the efforts of pressure groups to advance their respective political agendas. As with small political parties in a multiparty system, pressure or lobbying groups can wield a level of power disproportionate to their size, but this is a price democracies pay for the freedoms they guarantee.