Oh I see what you mean. Yes, you can use things like Chromecast to use your PC on your TV, but you can also directly connect your PC to your TV via HDMI or DisplayPort (though the first one is a lot more common on TVs). You can keep it offline in that case.
Some PCs and laptops might lack the HDMI port, but it’s pretty common. If you’re using a discrete GPU, you most likely have one. And if you don’t have one, you can get USB dongles for it.