Various definitions of its exact composition exist and no one definition is universally accepted. Despite this uncertainty in defining borders, it does have some important overall characteristics. For one, Central Asia has historically been closely tied to its nomadic peoples and the Silk Road. As a result it has acted as a crossroads for the movement of people, goods, and ideas between Europe, West Asia, South Asia, and East Asia.

In modern context, Central Asia consists of the five former Soviet republics of Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan. Other areas are often included such as Mongolia, Afghanistan, northern-Pakistan, north-eastern Iran, north-western India, and western parts of the People's Republic of China such as Xinjiang. South-western and middle China such as Tibet Autonomous Region, Qinghai, Gansu and Inner Mongolia, and southern parts of Siberia may also be included in Central Asia.

During pre-Islamic and early Islamic times, Central Asia was a predominantely Persian region that included sedentary Sogdians, Chorasmians and semi-nomadic Scythians, Alans. The ancient sedentary population played an important role in the history of Central Asia. Tajiks, Pashtuns, Pamiris and other Iranian groups are still present in the region. After expansion by Turkic peoples, central Asia became also the homeland for many Turkic peoples, including the Uzbeks, Kazakhs, Kyrgyz, and Uyghurs, and Central Asia is sometimes referred to as Turkestan.