Context in Odoo is used to pass data between views. By default, the context contains keys like active_id, active_model, lang, and company_id. Context can be used to set default values, filters, pass extra data, and define button behavior. Useful context keys include active_model, active_id, default_, search_default_, lang, active_ids, form_view_ref, tree_view_ref, search_view_ref and others to control views, filtering, and multi-company access.