I have a roku to give my TV streaming content. The roku I have has option for HDMI or older RCA ( left & Right Audio + 1 video plug as 3 plugs ). But my roku works over wifi for its internet connection.
There was an older model roku that had a RJ45 network jack to be hard wired. Most of them are wireless connected.
If you want it wired vs wifi, some DVD and Bluray Players also have streaming content option. My Sony Bluray player has a RJ45 jack for a Cat5 or Cat6 cable to plug into and it can connect to hulu, crackle, and other web streaming services.
I bought a chromecast when they first came out before buying my roku and I didnt like my chromecast because its not a stand alone device. In order to play content I needed to use my laptop or desktop computer and select to play something to which it would then show up on my TV, but in order to navigate and play content the computer had to be used. This meant that the computer couldnt be used for other things and when not needing the computer it was wasting electricity to serve up the casting of whatever its playing to the TV. I was going to sell my chromecast but found out that the only way i could do that would be if I sold my google gmail account with it because they are non-transferrable once registered to an e-mail account. So its somewhere at the bottom of a computer parts box to be thrown away some day as a waste of $39. If you have a phone that can connect to chrome cast and dont need to use your phone while watching TV, I suppose maybe the chromecast would make more sense for what it is. I got suckered into mine when everyone at work was talking about how great it was and I bought it just on that and that $39 isnt much money. I later found out the limitations and requirements and that it wasnt the greatest thing for me and that I cant sell it to get $20 of my $39 back as well as when looking at ebay people were trying to sell them used for $5 for people who didnt like them.
The roku is a stand alone device that just needs and internet connection and display to play the content on. I bought my roku on a business trip for $35 in oklahoma and used a trick of spoofing the mac address of it into my laptop assuming the same mac address for the wireless network adapter in the roku so that I could agree to the terms and conditions for 24 hours of free internet and start a lease for 24 hours for the roku's mac address. changed mac address back in laptop and turned my roku on and it got a lease with hotel free public network and I was instantly able to watch shows in which I watched lots of Big Bang Theory. The roku is very easy to set up with wireless. The small remote they give you has an easy to navigate system to set up a wireless connection and then its just a matter of watching a free service provider listed or register your roku with hulu or netflix or whatever service you pay for. A computer, Tablet, or Phone with internet access is needed to type in a confirmation code to link/pair the roku device with your account with that service provider such as R5XF7 typed into the website of whatever service displays this code on the TV, you type that into the website code confirmation and when done successfully the roku comes to life with that service providers streaming content unlocked. My Sony Bluray player also links/pairs hardware to my service by those 5 digit alpha numeric codes that display on the TV when establishing a connection to a paid for service.