On 03 Sep 2015, Ewald Böhm wrote in
alt.home.repair:

To watch youtube, you need a browser,

No, you don't. You just need an interface that will display Youtube
content. It's included with a smart TV.

which is usually a program
compiled for a certain computer, which runs a certain operating
system, and which has a certain byte order and memory structure
and a whole bunch of other things associated with a "computer".

That's all included in your smart TV.

Is the TV acting as a "computer"?

Yes.

If so, what operating system is the TV?

I assume it's some customized version of Linux, but it doesn't matter
unless you're planning to hack it. Normally you're given a user
interface that will allow you access to the features built into the
smart TV, which will include apps to access Internet content providers
like Youtube, Hulu, Amazon, Netflix, and others. It may also include
some games and other miscellaneous stuff. It may even include a web
browser (mine does, but it works poorly.)