As per the list
here, you can take four types of screenshots. Three of the four features of that tool are built into OS X.
1. Rectangular Snip: Shift-Command-4. Drag and release. Picture will be on your desktop.
2. Window Snip: Shift-Command-4 and when you see the crosshairs, push Spacebar. Your cursor will turn into a camera. Mouseover the window you want to capture and click. Picture will be on your desktop.
3. Full-screen Snip: Shift-Command-3. If you have a dual monitor setup (as I do), two pictures will be sent to your desktop, one for each monitor.
As for the Free-form snip, there is nothing like that built-in that I know of.