Wasabi, also known as "Japanese horseradish", is a hot Japanese spice root and an important member on any sushi table. Some like to mix it with soy sauce bowl for future dipping, and some rather place it directly on the sushi just before they eat

While wasabi is quite rare and expensive, so the general seen wasabi pastes are made of wasabi root, horseradish and mustard. the taste and flavor is almost the same as real 100% wasabi. so it's quite populous as a substitute of the rare wasabi.