I want to know what this feature does

[donghyunh26599689]

  This feature doesn't have any any name so I couldn't figure out what this does on my own through search engine.. Can someone tell me what this does?

Thanks!

[gener7]

This icon indicates a tablet-enabled feature. It represents a pressure pen on a pad, a Wacom for example.

http://www.tipsquirrel.com/5-awesome-icon-buttons-might-know-photoshop/

See the first on the list: "Always Use Pressure for Size"

[SJRiegel]

If you hover over it just right, it will tell you: