Short answers, pulled from the story.
The earliest stone inscription containing a recognizably Mahayana formulation was found in Mathura and dated to around 180 CE. This artifact bears a Brhmi inscription made in the year 28 of the reign of King Huviska for the Blessed One, the Buddha Amitabha.
Scholars have proposed the lay origins theory, the Mahasamghika origin theory, and the forest hypothesis to explain how Mahayana arose from early Buddhism. Recent scholarship by David Drewes challenges these theories, arguing that Mahayana was primarily a textual movement focused on the revelation and dissemination of Mahayana sutras within traditional Buddhist structures.
The Golden Age of Indian Buddhist Philosophy spanned from the beginning of the first millennium CE up to the 7th century and saw the rise of the Madhyamaka school founded by Nagarjuna and the Yogacara school promoted by Asanga and Vasubandhu. These schools engaged in fierce debates while developing concepts such as the Buddha-nature doctrine and the Prajnaparamita texts.
The central defining feature of a bodhisattva's path is the universal aspiration to end suffering for themselves and all other beings, a wish known as bodhicitta. This compassionate commitment distinguishes the Mahayana path from paths seeking arhatship or solitary buddhahood for one's own sake.
Mahayana texts and philosophy reached Central Asia and China through trade routes like the Silk Road before spreading to Korea, Vietnam, and Japan. Chinese monks like Faxian and Xuanzang traveled to India to bring back Buddhist teachings, and new developments in Chinese Mahayana led to traditions such as Tiantai, Huayen, Pure Land, and Chan Buddhism.
Vajrayana, also known as Mantrayana or Esoteric Buddhism, is a new movement that began during the Gupta period and drew on previous Mahayana doctrine along with new Pan-Indian tantric ideas. This form of Buddhism became dominant in Tibet, Bhutan, and Mongolia and remains an important part of East Asian Buddhism through traditions like Shingon and Mikkyo.