A simit seller on the Ceyhan bridge.

The Wikipedia, as usual, has some good info on the subject: A simit (Turkish), koulouri (Greek: κουλούρι) or Đevrek (Serbian: Ђеврек) is a circular bread with sesame seeds, very common in Turkey, as well as in Greece and other parts of the Balkans. The characteristics of simit (size, crunchiness/chewiness, etc.) tend to vary by region. In the city of İzmir, simit is known as "gevrek," (literally, 'crisp') although it is very similar to the Istanbul variety.

Simit is generally eaten plain, or for breakfast with jelly, jam, or cheese.

Simit and koulouri are often sold by street vendors who either have a simit trolley or carry the simit on their head. Street merchants generally advertise simit as fresh ("Taze simit!"/"Taze gevrek!" [in İzmir]); this is often not the reality. A general rule of thumb for obtaining fresh simit is to select a vendor with a large quantity, indicating that he has recently restocked his supply.