Badges are awarded to encourage and incentivize positive community actions within the site.
Badges (along with reputation) are what makes Stack Exchange sites tick.
If you have a question about how the badge system works, or a question about a specific badge, this is the tag to use.
A user may be awarded
Gold Badges are rare. You'll have to actively work toward these. They're something of an accomplishment!
Silver badges are awarded for longer term goals. Silver badges are uncommon, but definitely attainable if you're interested.
Bronze badges are awarded for basic use of Web Applications. They are easy to earn.
Some badges are awarded based on score. The term score means the total number of upvotes minus the total number of downvotes.
What surrounds a badge on the badge page?
The tick before the badge denotes that you've already been awarded that badge.
The number after the badges is the total amount of users the badge has been awarded to.
Want to know more?
Visit the Badges page for a list of available badges.
The FAQ: List of all badges with full descriptions, provides an intensive information regarding each badge, how it gets awarded, and exactly what it means.