Snap Objects to Other Objects Tool
In the Grid and Guides menu there is an option to "snap objects to other objects." This is an important tool to understand and use correctly. It is easily turned on and off by right-clicking anywhere on the slide (not on an object on the slide), clicking on Grid and Guides, and then clicking on the box next to Snap objects to other objects. Turn it off by unchecking the box.
This tool makes it easy to draw and align objects quickly and easily without having to align and distribute the objects. Don't work with this option on all the time, however. It will make other types of object placements on your slide tricky. Use it only when you have a need to create anything that needs precision placements quickly and easily.