Dashicons is an icon font that first shipped with WordPress 3.8. Since then, the core development team has routinely added new icons as necessary. WordPress 4.1 includes more than 20 new icons, specifically for the built-in media player and inline image editing tools.
There’s also a few miscellaneous icons including, a palm tree, tickets, a building, and money.
Dashicons are shipped with WordPress which makes it a convenient option for developers. They’re also licensed under GPLv2, or any later version using the font exception. To request a new icon, keep an eye on Trac for the ticket that covers WordPress 4.2.
If you encounter an issue using Dashicons, please create a new ticket on trac. Use the “administration” component and the “UI” focus when creating the ticket and be sure to include “Dashicons” somewhere in the text of the ticket.
What other icons would you like to see added? Also, in what circumstance does it make sense to use the palm tree icon?