6. The Tools in the Toolbox / 6.2 Tools for All Kind of Layers
The moving hand is used to move the visible part of a picture.
Of course this is only useful, if the picture is larger than its window.
The moving hand has the option Move/Zoom synchronously to move and zoom all open documents synchronously. All documents will show the same position, too.
For faster access you can activate the moving hand by pressing and holding the space bar. On Windows you can use the moving hand by clicking and holding the middle mouse button, too. By holding Shift all documents will be moved synchronously.
Double clicking the moving hand icon adjusts the window size to the containing picture.