ELI5: Explain Like I'm 5

expansion slot

An expansion slot is a place in your computer where you can put extra parts. It's like an extra space for your computer that helps it do more things. For example, if your computer only had one monitor, you could add another one through an expansion slot. Or if your computer wasn't very good at playing games, you could add a graphics card to the expansion slot to make it better at playing games. The extra parts are called expansion cards, and they go into expansion slots.