Autonomy is the condition of something that does not depend on anything else.
In Eastern Christianity, autonomy is the status of a hierarchical church whose head bishop is appointed by a higher-ranking bishop, often a patriarch, who has no other authority over the autonomous church. This status is one step short of autocephaly.
In politics, a self-governing city or region, e.g. Kurdistan, Kosovo or Hong Kong SAR (not necessarily as a result of formal secession), is autonomous. True autonomy is usually a pre-requisite to separation or secession, however, but autonomy does not necessarily lead to separation. Autonomy is not independence.