Those stars indicate how good people are at answering questions.

The more stars you have, the better your answers have been rated by other visitors.

Here's how it works: Every time you write an answer you get 10 points. Each time an answer you've written gets a thumbs up, you earn 10 more points; each time an answer you've written gets a thumbs down, you lose 10 points.

Every night, the system adds up everyone's points and updates their stars accordingly. The top 20% of users get five stars, the next group gets four stars, etc.

If you're interested, here's the scale:

more than points: 80%-100% (i.e. the top 20% of people who've answered questions) =
60%-80% =
40%-60% =
20%-40% =
0%-20% =