A Yatai (屋台) is a small street food stall.
They tend to specialize in a single product like ramen, yakisoba, yakitori, takoyaki, okonomiyaki and a lot more. However, the menu is not limited only to Japanese cuisine. Korean, Chinese and western food Yatai are also common. Usually the food stalls dish are from 300 to 600yen.
Matsuri (Japanese festivals) are a common place to enjoy food at a Yatai, but that is not the only place where you can find one. Yatai are also set up on pedestrian walkways in the evening and are removed late at night. Businessmen and their coworkers usually use them to relax over dinner and have some drinks on their way home from work.
And of course there are Yatai that sell sweets too!