Quick Facts

Terrain

Mostly rugged mountains; plains in north and southwest. The Hindu Kush Mountains that run northeast to southwest divide the Northern provinces from the rest of the country; the highest peaks are in the northern Vakhan (Wakhan Corridor). Hindu Kush translates as "killer of Hindus".

South of Kandahar is desert.

Elevation extremes 

Lowest point: Amu Darya 258 m
highest point: Nowshak 7,485 m

Ethnic groups

Afghanistan is a very diverse country ethnically. Tribal or local allegiances are strong, which complicates national politics immensely.
The two largest linguistic groups speak Pashto and Dari (Afghan Persian). Pashto speakers predominate in the South and East, Dari in North and central Afghanistan.
About 11% of the populations have Turkic languages, Uzbek or Turkmen, as their first language. Many of them are in the North, near Uzbekistan and Turkmenistan.
Baluchi tribesmen, still largely nomadic, can be found anywhere between Quetta in Pakistan and Mashad in Iran, including much of Western Afghanistan. They make marvelous, if often somewhat simple, rugs.
Hazaras in the Central mountains look much more Asiatic than other Afghans. They are descended from Ghengis Khan's soldiers.

Languages

Dari, very similar to Persian, is the native language of half the population, Pashto of 35%, Turkic languages (primarily Uzbek and Turkmen) of 11%. There are also 30 minor languages such as Balochi. Dari is the historical lingua franca, but in the South and East Pashto is more common. Most people speak more than one language. You'll find a few people in Kabul who speak a little English but otherwise it isn't widely understood.