How is this redirection possible?

The new domain that I purchased has a redirection from channel4.com.

The page it gets 301 redirection from is like this channel4.com/website and it redirects to my website.

How is it possible and is it good for SEO?

It's not bad, the only problem is that it has 0 OPR, the only good thing is that you can build rep on top of that redirection as you would do with a parasite.