Lock-down VM. What does this mean?

Hi,

I'm not wanting a detailed discussion. I am only asking what it means to secure a host ruing a vm. To jail the vm if you will so, that it is isolated and it is more difficult for it to pass things malicious to the host. In my case, using KVM on my desktop machine to run vm's.

What might I use this for? Skype, safer browsing, to banking sites possibly, data streaming from paid for providers like, NHL.com. I duo what all I would use it for in the future when, I retire. I just like the idea of leaing about isolating OS's in such an environment for the safety of it. Who knows, in my free-time in retirement, I might want to make it easier for myself to use paid for services in a Windows vm that are easier to set up than, wrestling with trying to safely set the same services in Linux and not put my Linux host at risk? I have to admit for now, my entertainment part of my Linux computing is all but non-existent and I only use Xubuntu, and will never want to willfully insecure my Linux installs.

So, what does this mean? No coectivity to WHAT on the host? And what/where can I read about what, "locked down" means?

Thanks, for any Idea.