There are different types of ticket classes available for traveling from Tokyo to Hiroshima on the Shinkansen bullet train, such as:
Ordinary Car
Every Shinkansen train includes standard cars known as ordinary cars. These are the regular, economy-class seats on Shinkansen trains, providing comfort and enough legroom. Typically, these seats are set up in rows of 3+2. Another term for this class is second class, offering affordability along with comfortable seating, sufficient luggage storage, and generous legroom.
Green Car
Similar to first class, Green Cars provide enhanced comfort, space, and a quieter vibe. These cars are more comfortable compared to Ordinary Cars and are defined as first-class travel in Japan. Easily recognizable by a four-leaf clover symbol, Green Cars make sure you have a premium experience across Japan's Shinkansen network, including iconic trains like the Nozomi and Mizuho connecting Tokyo and Osaka, as well as the Hokkaido Shinkansen. Some Nozomi trains even offer complimentary drinks, snacks, and newspapers onboard.
Take note that Green Cars are not available on most Hikari and Kodama trains on the Sanyo Shinkansen line, some Sakura and Tsumabe trains on the Kyushu Shinkansen line, and all Kamome trains on the Nishi Kyushu Shinkansen line.
Gran Class
If you want an extraordinary train experience, consider trying the luxurious Gran Class option on select Shinkansen trains. It's not offered on many trains, which makes it even more special. This special option is available on newer Shinkansen models like the Hayabusa E5 Series and E7. You get a fancy train car with lots of seating and personal attention from a host or hostess.
Keep in mind that the Nozomi trains do not include the Gran Class. The Gran Class is available only on the Tohoku and Hokuriku Shinkansen trains. The most luxurious class on the Nozomi is the Green Car.