Slums are overcrowded, poverty-stricken areas lacking open spaces and healthy housing. They form due to factors like industrialization, lack of zoning laws, and migration to cities. Slums are characterized by inadequate access to water, sanitation, and other infrastructure along with poor housing quality and overcrowding. Efforts to reduce slums include slum clearance and improvement programs which aim to demolish unsafe structures, widen roads, and provide amenities to improve living conditions for slum residents. Preventing new slum formation requires measures like ensuring affordable housing and maintenance of buildings.