What you are describing is called a monopoly.
A monopoly is when one company or entity controls an entire share of a market. For example, if Apple became the only company you could buy a cell phone from, this would make Apple a monopoly. Monopolies can hurt the American economy, as a business with no competition can essentially charge whatever they want for a good or service since there will be no business who will offer a better prices.
The government is the political/bureaucratic system that runs the state. A state is composed of territory, population, sovereignty.
Answer:
Political parties today have lots of jobs/roles. One role of political parties today is making and passing laws. Another example is parties can link their members at different levels of government to achieve big goals for the party like winning elections or organizing fundraisers.
Hope this helps!