Sushi is a kind of Japanese cuisine which is consisted of vinegared rice combined with other ingredients which is usually seafood. That's why people said that sushi is not for vegetarian people. However, there are also sushi which is actually made with vegetarian ingredients such as carrots, cucumbers, etc. Of course, the ingredients depend on yourself.
There are many kinds of sushi, such as: Makizushi, Nigirizushi, Temakizushi, etc.And probably the most common one is Makizushi. The black seaweed is also commonly used in sushi. To know more about how to make vegetarian sushi, just watch this video.