What are strainers used for at the top of a downspout?

Strainers are installed at the top of a downspout to prevent debris such as leaves, twigs, and dirt from entering the downspout and clogging it. Clogs can cause water to overflow the gutter and pool around the foundation of the house, which can lead to water damage. Strainers also help to keep the downspout clean and free-flowing, which is essential for proper drainage.