Dashicons is the official icon font of the WordPress admin as of 3.8.
The Dashicons project is no longer accepting icon requests. Here’s why: Next steps for Dashicons.
For any issues that appear within WordPress core, please create a new ticket on trac. Use the “administration” component and the “UI” focus when creating the new ticket, and be sure to include “Dashicons” somewhere in the text of the ticket.
Dashicons is licensed under GPLv2, or any later version with font exception.