For questions about tags which are sponsored (have an icon on them) and how tags can become sponsored.

What does an icon on the tag mean?

Tags with icons are sponsored tags. They cost money to sponsor, not reputation on the site. You can figure out more info on how you can sponsor these tags by checking out the advertising info link in the footer. - Grace Note

How do you sponsor a tag? How much does it cost?

You should contact the Advertising department of Stack Overflow. The contact form is at https://stackexchange.com/about/contact (linked in the footer of each site as advertisement info and you should mention you are interested in sponsoring a tag. This includes the icon, but also a list of sponsored links (See the Android Tag page for an example). - Michael Stum

Do sponsored tags get ranked higher?

Sponsored tags have no special logic attached to them. - Jeff Atwood

Is there a way to see all “Sponsored Tags”?

A "sponsor gallery" is on the to-do list. - Alex Papadimoulis