떡 means rice cake. As a food, 떡 has great cultural significance in Korea. It is part of the menu on a child’s first birthday and part of a soup on New Years Day. It is also used in a variety of desserts and snacks. Many stores specialize in selling 떡. Below are some examples.
Of course, the most widely seen usage of 떡 is in the popular snack called 떡볶이, rice cakes covered in a sweet and spicy red sauce, widely sold at street vendors (포장마차).