Ghacks takes a look how DPI Scaling works in Windows 8.1
Most Windows users probably do not bother with their operating system's DPI scaling settings at all. The setting determines how items on the screen are displayed which is independent from the screen resolution the monitor is running on. Some users like to increase the DPI scaling to improve the readability of elements on the screen.How DPI Scaling works in Windows 8.1
The main purpose though is to make sure that items on the screen look fine regardless of resolution and size of monitor. A basic example is that the items on the screen of a 24" Full HD display may look different than items on a screen of a 46" Full HD TV if the same DPI setting is used. Basically, the items will not appear at the same scale when you compare them, with items on the 46" considerably smaller than those on the 24".
