Enlightenment and Nirvana for Gautama was very simple, he got it "in a flash" under the Bo tree, after sitting in meditation for 7 weeks, and life's problems were no longer an enigma to him.
    But it is not so simple... the many followers, traditions, branches and sects found out they need years of hard work, and thousands of Buddhist monks and nuns dedicate their whole life with vows of poverty, celibacy, and obedience to obtain it... and, most often, after all that hard work, they reincarnate again and again, the greatest curse for a Buddhist.       

    1- Hinayana, Lesser Vehicle, (Theravada): Emphasizes the writings of the Buddha, the closest to Buddha's original teachings, in southern Asia, Sri Lanka, Burma, Thailand, Cambodia.
    2- Mahayana, Greater Vehicle: emphasizes the spirit of Buddha, by far the largest branch of Buddhism, in China, Japan, Tibet, Korea, Nepal, Indonesia, Vietnam, Sri Lanka, Thailand.
    Mahayana introduced the doctrine of "bodhisattva"or "helpers": Enlightened perfect beings who become gods, which is an open rebellion against the teachings of Gautama Buddha.
     3- Vajrayana, Diamond Vehicle, the third Vehicle, Tantrism. It borrows the Hindu belief in the goddess Shakti sexual power and developed a cult devoted to idols, magic and sex. It has been condemned as a degeneration of Buddhism, and indeed it is an anti-Buddhism.
     4- Tibetan Buddhism: In Tibet and Japan, added to Tantrism the primitive animistic religions of the Tibet, the magic "bon", and some "Mahayana" doctrines to create the most openly occultist of all Eastern religions. On top of it created the super-authority of the "Dalai Lama", a god-on-earth, heading a hierarchy of priests, destroying the "religion without authority" that Gautama the Buddha proposed.  
     5-Nicheren Buddhism: In the 13th century a Japanese, Nichiren, founded a school whose aims are the opposite of Gautama Buddha: To satisfy all desires, because "happy individuals can build a happy world"; with emphasis on acquiring wealth, power, personal happiness, pleasures, political power...
     6- Pure Land (Sukhavati, Jodo, Ching-tu): One enters the Pure Land through faith in the god Amitabha, or Amida or Buddha,  by repeating the "membutsu", "Namu-Amida-Butsu",  "Have faith in Amida, and you will be saved", they proclaim, imitating Jesus Christ... in a total contradiction of the teachings of the Buddha.
     7- Zen Buddhism, from Japan had become in the mid-20th century perhaps the best known of the Buddhists schools in the Western world... "Zen" means "be nothing, think nothing", and "Zazen" "seated meditation"; its adherents claim Zen to be the quintessential of Buddhism... and it may be a real Buddhism, not an anti-Buddhism.
     8- "Folk" Buddhism: Besides the "official" Buddhism, there is the "Folk" Buddhism, very popular. It is "animistic", with magic to spell spirits and devils, with many gods, divination, witchcraft... and it is lived with Taoism, Confucianism or  Shintoism...
     - Finally, Hinduism: The Buddha, for the Hindus, is the 9th incarnation of Vishnu... of course, openly against the will and teachings of Gautama Buddha himself... The 7th and 8th incarnations of Vishnu for the Hindus are Rama and Krishna... and the 10th incarnation and the last one, will be "Kalkin", still to come. .