I do not have it but Roku is a small box you can add to your home theater setup to be able to stream content from various sources to view.
What Is Roku? FAQS

What is Roku?

those links should help explain it including pictures of it

Roku uses your internet connection. It's just one way of streaming media over an internet connection - others are a "smart" Blu-Ray player, a "smart" TV, or a game console with streaming capabilities, like XBox or Wii (though Wii doesn't stream in HD). It's just like watching a Netflix movie or Youtube video on your computer, except that it's a way to get it to your television.

Personally, we opted for a smart Blu-Ray player, because it will play DVDs and Blu-Ray discs (though we have none of those!) in addition to streaming from online sites. Last year, we paid about $200 for the Blu-ray player, but I see them all the time now for under $100.

We have one because some friends gave it to us. We just hook it up to the internet and the tv. It has all sorts of "channels" you choose and then can scroll through. Netflix, Amazon "Watch Now" or Prime, Pandora, tons of different movie channels, radio channels, etc. Some things are free and some things cost money. I listen to my Pandora radio on the tv while doing housework. I order movies to buy and rent off Amazon and watch them through the Roku. If you have netflix streaming, you can watch anything from there, etc.

My sister just bought a Blu-Ray that does the same thing and she loves it. There are many options of getting internet over your tv, this is just one way. A lot of new tvs have it built in now also.

I have Roku; it was a gift one Christmas from my son-in-law. It's a small box he hooked up to my TV, and has its own remote.

I use it to stream Netflix, and love it! (He gave me the Netflix subscription too.) I set up the Netflix Instant Queue on my computer, and then select what I want to watch from the TV, using the Roku remote. It has nothing to do with my TV reception, because it doesn't bring in a TV signal. (I have an antenna, BTW, but that doesn't factor into streaming Netflix.)

Roku is not expensive and works very well for me.

I have a Roku. The company I work for has a wireless chip inside it so our design department were all given a Roku for Christmas a couple years ago.

Easy peasy to set up and use. I stream Netflix but there are other services to choose from as noted above.

Jodi-

We have had one for about six months. We also have a TiVo hooked to the same TV. For the most part, we use it to stream Netflix, but since I am also an Amazon Prime member, we can get free streaming videos that way, too. I bought ours from Amazon for $50. My son has a very similar device called Apple TV...it works the same way, pretty much, but his cost $99. He can also view items thru his Apple Tv box that originates on his iPad. Yes, you do need a computer network for either one, though we actually WATCH on the TV, not the computer.