What is ultimate exactly? Is that a shorter name for ultimate Frisbee or something? 
Yes that's correct, ultimate frisbee  is a non-contact team sport played by players with a flying disc 
I've noticed that the ultimate frisbees are a lot heavier and are made of different material than regular frisbees.
I'm not sure about that by I can tell you that the sport have been on since 1968 and was developed by high school students
1968? Wow that has been around for quite a while for such a modern sport.
Yes and also it's just like every other sport out there because it focuses on self-officiating, even at the highest levels of competition.
It really surprises me that high school students developed such a big sport!
the Wham-O toy company, and thus the sport is not formally called "Ultimate frisbee", though this name is still in common casual use. Points are scored by passing the disc to a teammate in the opposing end zone. Other basic rules are that players must not take steps while holding the disc, and interceptions, incomplete passes, and passes out of bounds are turnovers. Rain, wind, or occasionally other adversities can make for a testing match with rapid turnovers, heightening the pressure of play.
Ultimate in Japan
Ultimate, originally called ultimate frisbee, is a non-contact team field sport played with a flying disc, invented in New Jersey, USA, in 1968. Japanese players and teams rose to prominence in the 1990s, and today are among the strongest competitors in the sport globally.
History.
The frisbee was introduced to Japan in 1969. Japan Flying Disk Athletic (JFA) was established in 1975 in Nagoya, and started meeting in 1976. In 1984, JFA changed its name to JFDA