I just got a new smart tv, and in the ‘input’ list it shows folders on my laptop. So I’m guessing my laptop is sending signals to my TV.
Does this communication between my laptop and TV only extend within my password protected wifi, or can neighbors see inside my laptop? I assume the latter, but don’t know a lot about this.
Either way, how do I turn this function on or off?
Assuming Win7 – to turn off sharing - here
If you want to nuke it from orbit you can disable the server service.
-go to services (start, type in services)
-find the service named ‘server’ and go into it
-click stop, set the startup type to disabled then ok
The former, but I expect that is what you really meant. 
You’re fine, unless they crack your wifi password.
Just disabling Sharing or the Server service may not be enough. If you set up Windows Media with a library, you may be sharing your Windows Media libraries via DLNA/UPnP, yet another ad-hoc sharing protocol that is specific to Digital Media. Again, this is not visible outside your internal network.
I have not tried this, but this link tells you how to disable DLNA sharing.
Si