Rotate 3D 
Using this button you can rotate the model/object. When you activate this button a circle appears on your screen and you can rotate the model/object pressing the left button of the mouse and moving it towards the direction you want.
Depending on where you place the cursor according to the circle, the rotation type changes as well as the cursor’s shape. There are the two following cases:
Placement of the cursor in the circle.
If you press the left button of the mouse while the cursor is in the area inside the circle and move the mouse keeping its left button pressed, you can rotate the model in three dimensions.
Placement of the cursor out of the
circle.
If you press the left button of the mouse while the cursor is out of the circle and move the mouse keeping its left button pressed, you can rotate the model around the level that is defined by x, y axes.