Precisely what 'open' means in open education has been the subject of some debate. Contemporary education as a whole may be broadly understood as incorporating a wide range of pedgogical and scholarly activities which can take place inside or outside formal institutions. Very broadly, these can include:
learning, whether through instruction, guided activity or self-directed learning;
teaching which can include mentoring and all non-instructivist activities around the deliberate nurturing of knowledge;
assessment which may be any combination of summative, formative and/or diagnostic;
accreditation which can include recognising learner or educator accomplishment;
policymaking at any level of education or governance where this influences curriculum, funding and procedures in education; and
administration, dealing with recruitment, admissions, retention, progression, graduation, timetabling, reporting, and management.
In a traditional learning environment (such as a school or university) these aspects of practice tend to relate to each other in familar ways. When we talk about open education we're really interested in the ways in which our practices can change as a result of adopting open practices, but also in education outside of formal institutions.