When is the last time you thought about the Press & Drag function? If you are like me, it was probably when I read Steve Stafford's Revit OpEd blog when he discussed Revit 2014's selection features
For Revit 2013 and previous, the Press & Drag (Figure 1) button is located at the bottom left corner of the Revit User Interface. It can be enabled and disabled by clicking the checkbox.
Figure 1 - Press & Drag (Revit 2013 and earlier)
In Revit 2014, Press & Drag has been renamed Drag Elements on Selection (Figure 2). It can be enabled and disabled by clicking on the icon (Figure 2) or by clicking on the Modify dropdown button and checking or unchecking Drag Elements on Selection (Figure 3).
Figure 2 - Drag Elements on Selection
Figure 3 - Turning on and off Drag elements on selection
By default, Press & Drag is checked (enabled). When checked it will allow you to Press and Drag any object with one click. In short, it is a shortcut to moving an object.
Press & Drag can be annoying when you accidentally move an object, when you simply just intended to select the object to perform some other action. If this happens, then you can uncheck Press & Drag. If you still want to move the selected object, you simply have to click a second time to drag (move).
My preference is to always have Press & Drag enabled, but that is a personal preference.