Whole range of educational activities, taking place in various settings, that aim to meet basic learning needs as defined in the World Declaration on Education for All (Jomtien, Thailand, 1990). According to ISCED standard, basic education comprises primary education (first stage of basic education) and lower secondary education (second stage). It also covers a wide variety of non-formal and informal public and private activities intended to meet the basic learning needs of people of all ages.
(http://uis.unesco.org/en/glossary)
The foundation for lifelong learning and human development on which countries may build, systematically, further levels and types of education and training.
Source: UNESCO 1992
Basic education typically comprises primary and lower secondary education, and increasingly one or more years of pre-primary education. It usually encompasses compulsory schooling.
(http://www.ibe.unesco.org/en/glossary-curriculum-terminology)