A coalition government is formed when multiple political parties collaborate to govern, usually arising when no single party achieves an outright majority in a legislature. This arrangement allows parties to work together, often to create a stable government by combining their resources and support. Coalition governments are common in parliamentary systems, where collaboration is necessary to achieve legislative goals. Such governments can lead to broad representation and more comprehensive policy-making but may also face challenges like internal disagreements and difficulty in maintaining unity due to differing party ideologies.