Kachru's theory divides the varieties of English used globally into three circles - the Inner Circle consisting of countries where English is the primary language, Outer Circle where it is widely used as a secondary language, and Expanding Circle where it is used predominantly as a foreign language. Studies estimate there were 375 million users in the Inner Circle, 375 million in the Outer Circle, and 750-1000 million in the Expanding Circle as of 2001. English spread from Britain to its colonies and also serves administrative purposes in countries it was adopted in after colonization, contributing to its global influence.