DC-DC converters are electronic devices used to convert one DC voltage level to another, typically with higher or lower voltage levels. They are essential in various electronics applications where power requirements differ from the available power source. DC-DC converters come in different topologies such as buck, boost, buck-boost, and flyback converters, each suited for specific voltage conversion needs. They find extensive use in battery-powered devices, renewable energy systems, automotive electronics, telecommunications, and industrial applications.