What are expansion slots used for in a computer?

Expansion slots in a computer serve as interfaces on the motherboard that allow for the addition of extra components or cards, enabling the computer to expand its capabilities. The correct answer focuses on the role of these slots as electrical connectors, which is key for integrating various hardware components.

When additional cards, such as graphics cards, sound cards, or network cards, are inserted into these slots, they connect electrically to the motherboard, allowing them to communicate with the computer's processor and other components. This electrical connection is crucial for the functionality of the added hardware, supporting their operation within the system.

The other responses reference functionalities that do not precisely align with the specific purpose of expansion slots. Expansion slots do not directly connect peripheral devices; rather, they are for internal cards that may, in turn, connect to peripherals. They do not house the power supply, as that component has its own designated location. While expansion slots can influence data transfer rates by housing specific components that enhance performance, that is a secondary effect related to the type of card being used rather than a function of the slots themselves.