Regions in code break up a code and make it easy to look thru.
CTRL+M CTRL+M (that's two key presses!) - collapse/open the current parent region
CTRL+M CTRL+L - Collapse/Open all regions in document recursively (meaning you might get only one line in the document - one big namespace region which is collapsed or you'll see the entire page code uncollapsed
CTRL+M CTRL+O - Collapse all regions not recursively