It will depend on whichever tv package you have signed up to. But its main purpose is to stream big new tv shows online first. I imagine this is linked to them offering an ad free service for which you have to pay.
But in the meantime if you have a computer and a tv nearby you just need to connect the two as discussed above.
This is what the Radio Times has said:
You can already explore what ITVX has to offer by heading to itv.com to check out the web browser version. If you have a Samsung Smart TV (dating from 2016 onwards), an Xbox One/S/X or Xbox Series X/S, a Huawei device, a Chromecast, a Roku streaming player or a NOW smart stick or box, then your app should have updated too.
Otherwise, you’ll have to wait for the ITVX app to replace the old ITV Hub app on your device.
www.radiotimes.com/tv/itvx-start-date-prices-shows/