It is the path by which an organisation moves from working in CAD, or with improvised BIM, to producing and managing information models under its own rules: digital strategy (why, and for which projects), processes (who does what), tools (software, templates, libraries, common data environment), people (roles and training). It is not a course and it is not a licence purchase: it is a change of method, measured on projects.
A serious BIM implementation plan takes months, starts from a pilot project and produces standards that stay with the organisation.