Solution:When power changes between two parties in a country, the party system is called a two party system.
In countries where a two-party system exists, power changes between them only. The two major parties have a high chance of winning and forming a government. When compared to a one-party system, it accommodates more ideas and interests. Even though other parties exist, they can win only a few seats and are not eligible to form a government. The primary examples of a two-party system are the United States of America (democratic party and republican party) and the U.K(labour party and conservative party).