Joomla FrameWork ::

I am trying to understand how the joomla framework works, i see an heavy usage of " :: " in its code, here an example: function edit () { JRequest::setVar('view, 'single'); $this ->display(); } from my really basic php understanding in the function edit i call a function setVar() and i pass the paramter 'view' and 'single' in it then the output ($this) is passed to the display() function. My question is what does :: means? an more precisely referring to the example: JRequest::setVar('view, 'single'); how do you read it and how do you manage it? Cheers, Nick