Change the visible property of the text box from the view model ( WPF, MVVM)

Hi,

I am a beginner here in WPF and MVVM. I have certain controls on a window in my project. For example, I have a text box in my window. I am using MVVM Pattern and here I want to change the visible property of the text box from the view model. 

One other thing is that, I want to change the visibility of the text box from the viewmodel based on some conditions.

Well, I googled it and google throws me some suggestions which were all different solutions and I'm in a total confusion. 

Guess some one can help me figure this out. 

I know this would be a piece of cake for the WPF MVVM Experts, but since I am trying to learn this stuff I require some code as examples.

Thanks