Cotton (Gossypium) is a shrub that belongs to the mallow (Malvaceae) familiy like okra and hibiscus.

Depending on how it is cultivated cotton grows 25 cm to over 2 m high. Cotton flowers are white or yellow when they open, turning pink after pollination. The pods of the pollinated flowers open after a couple of weeks and the hairy cotton seeds spring up. Every cotton boll contains about 30 seeds, each of which has 2000 to 7000 seed fibres. Cotton is normally grown in annual cultivation. Only in a few regions in South America (Peru, Brazil) cotton still grows on perennial bushes. Depending on climate and cotton variety, the cotton plant needs 175 to 225 days from sowing to maturation.

Further reading:

Bremen cotton exchange, cotton in brief

ICAC, cotton facts, R. Chaudhry et al.

Wikipedia