It’s part of the holy trinity of MS-DOS hardware configuration settings: port, IRQ, DMA channel. When you installed a card like Sound Blaster so your PC games

It’s part of the holy trinity of MS-DOS hardware configuration settings: port, IRQ, DMA channel. When you installed a card like Sound Blaster so your PC games could actually play some passable music and sound effects, you’d configure these settings with physical jumpers on the card. And then you have to pass those configuration settings to the game somehow so it can send data to the device. You could leave the card to its default settings, but then it might collide with another device like a printer or whatever.