[rab] It's a web streamer you control with an Android device or (to some extent) a chromebook or the chrome browser. Essentially most things you can do on your Android device you can 'cast' to your TV. It's a bit like a dumber Apple TV, one that doesn't have its own onboard apps but just plays what some other device sends it (or tells it to play -- the distinction is blurred).

Depending on whether the app's media type and location is supported by Chromecast, the 'source' device may actually be doing the work of fetching and rendering the material and 'casting' the A/V output to Chromecast, but commonly it's just sending the URL and various tokens and chromecast is doing the actual fetching/decoding.

It's similar to having an Airplay-only device on your TV; bearing in mind that they are similar protocols but not the same nor interchangeable. Its main disadvantage is that it can't play content that's local to your network, so if you have your own movies and things you have to play them on your device and screencast it to chromecast. Which may or may not be well supported and look decent. For several good reasons I'd rather tell the TV-attached gizmo "play this file, which you can find over on that computer", than tie up some other device playing it and throwing the video to the TV. You can do the latter with Apple TV as well, but the thing is you don't have to, at least for any content that's supported by iTunes.

There's a metric shedload of other ways to do this sort of thing, with various amounts of overlap and wheel reinvention. The Apple TV approach is one I recommend for someone who's already pretty invested in the Apple ecosystem. It's probably the quickest route to maximum versatility without going to a lot of expense or trouble. If you don't have least one iDevice and/or don't want to use iTunes for your local media, getting as complete a solution can be a little more complicated, though not necessarily more expensive and there are a few reasons why it might be worth the trouble.

[Raak] Sorry, I could have sworn I read your post as saying you intended to connect a disc player. Ignore HDMI cabling entirely.

[Stevie] I thought TVs all ran over HDMI these days? I do have a DVD player (other than my computers), but it and the TV are both so old they use SCART.

[Raak] You said you were going with a network-to-TV model. A smart TV will hunt for your network, ask for a password and then present you with whatever app-based interface it uses so you can start consuming content. No wires other than the power cable. You want to push a signal in over a wire, HDMI is the best way (but not usually the only way on a decent TV). You want to take the sound to somewhere it sounds decent (thin tellies mean small speakers, no resonant cavity and crappy sound) use an optical link (over a cable) to a soundbar for the most compact solution. You can buy a receiver later if you decide you need better sound.