Live Streaming & Premieres
Capture card
Also called: video capture device
A capture card sits between the thing making the picture and the machine running the stream. Console gameplay, or a mirrorless camera being used as a webcam, arrives over HDMI and comes out as a source inside OBS. External cards connect over USB and internal ones into a PCIe slot on a desktop.
Passthrough is the feature to look for when capturing a console or a second computer, because it sends the picture straight on to your own monitor with no added delay while the card feeds the stream separately. Each card has its own resolution and frame rate ceiling, and that ceiling applies whatever the source is capable of outputting.