Short answers, pulled from the story.
Gandhara was located in present-day northwestern Pakistan and northeastern Afghanistan. Its core was the Valley of Peshawar, but its cultural influence extended across the Indus River to Taxila, westward into the Kabul Valley as far as Bamyan, and northward to the Karakoram range, including the Swat and Bajaur valleys.
Gandhara reached its cultural and political peak during the reign of the Kushan king Kanishka the Great, who ruled from 127 to 150 CE. This period, sometimes called the Golden Age of Gandhara, saw the flourishing of Gandharan art, the spread of Mahayana Buddhism, and the construction of the 400-foot Kanishka stupa at Peshawar.
Gandharan art is a distinctive style of Buddhist sculpture that blends Hellenistic artistic elements with South Asian religious imagery. It is notable for being among the first traditions to depict the Buddha in human form, and for producing images such as the youthful Buddha with wavy curls resembling statues of Apollo. The tradition flourished from the 1st to the 5th centuries CE before being destroyed following the Alchon Hun invasions.
Gandhara served as the central location for the Silk Road transmission of Buddhism to Central and East Asia. As early as 147 CE, the Kushan monk Lokaksema began translating Mahayana sutras from the Gandhari language into Chinese, producing the earliest surviving Chinese versions of key texts including the Astasahasrika Prajnaparamita Sutra.
The Alchon Huns launched destructive invasions beginning around 430 CE, systematically destroying Buddhist monasteries and stupas, including the famous Kanishka stupa at Peshawar in the 460s CE. The Alchon ruler Mihirakula is recorded in Buddhist sources as ordering the destruction of more than a thousand monasteries. Buddhism never recovered, and the name Gandhara disappeared after Mahmud Ghaznavi's conquest of the Hindu Shahi Kingdom in 1001 CE.
The primary language of Gandhara was Gandhari, a Prakrit or Middle Indo-Aryan dialect written in the Kharosthi script, which derived from the Aramaic alphabet. Gandhari spread across South and Central Asia during the Kushan period and died out around the 4th century CE. Among modern languages, Torwali is considered to have the closest linguistic affinity to the ancient Gandhari dialect.