FEATURES

Region mode

Activate region mode by hitting the Print key on your keyboard or by choosing Capture region from the context menu.
Left-click and drag to define a rectangular area you want to be shot.
After releasing the mouse button, the image editor window will open for further editing of your screenshot.

For shooting the region again later, choose Capture last region from the context menu.

Window mode

Activate window mode by hitting Alt + Print on your keyboard or by choosing Capture window from the context menu.
Click the window you want to be shot.
After clicking, the image editor window will open for further editing of your screenshot.

Fullscreen mode

If you want to shoot the complete screen, just press Ctrl + Print on your keyboard or choose Capture full screen from the context menu.
The complete screen will be shot instantly, the image editor window will open for further editing of your screenshot.

More features on the official Greenshot site