Charts are a visual representation of data, and when seen on a PowerPoint slide from afar, you make out the value of a series by exploring where exactly it’s placed vis-à-vis the axis. Of course, if your chart has data labels, then this is less of an issue — however, typical charts may have no data labels. For such a chart, the Tick Marks placed on the axis will help us get a better idea. Most chart types show two types of tick marks on axes — Major and Minor.
Learn about the Tick Marks, both Major and Minor on chart axes in PowerPoint 2011 for Mac.

