Connect 1 HDMI source to multiple screens.
You use an HDMI splitter if, for example, you want to play games on your TV one time and on a large screen the other time. You don't have to change cables, this is done automatically.
Connect multiple HDMI sources to 1 screen.
You use an HDMI switch if you want to connect multiple devices to your TV with just 1 cable OR if your TV has fewer HDMI inputs than desired.