The term Strata has many different meanings, depending on context. The term is used interchangeably to refer to a building or complex of buildings with more than one separate owner, Strata Management, the Owners Corporation or the Strata Committee. Colloquially and most commonly, however, it simply means a building with multiple separate owners.
Strata "Scheme" - the Building
A Strata Scheme refers to the building, and applies to any building or complex of buildings where parts of the land are owned by multiple different parties. For instance, in your typical apartment building, every unit owner owns their lot, and also owns a portion of common facilities like the roof/foyer/basement, driveway/garage, stairs/elevators, and infrastructure like the switchboard and water/sewerage pipes. This collectively owned portion is called 'common property'.
A Strata Scheme, in the context of the building, can also be referred to as a Scheme, building, complex, 'the Strata', or Strata Title.
Owners Corporation - the Legal Entity
The Owners Corporation is the name for all owners, collectively, as well as the legal entity representing the Strata Scheme. If the Strata Scheme is a nation, the Owners Corporation is the citizenry. The Owners Corporation is the ultimate authority within a Strata Scheme, and certain decisions - like appointing a Strata Committee, changing the appearance of the Scheme, approving major renovations or appointing a Strata or Building Manager - must be made by the Owners Corporation at a General Meeting.
Strata "Committee" - the Governance
A Strata Committee is a group of people, usually (but not always) lot owners, who make interim or day-to-day decisions on behalf of the Owners Corporation. If the Strata Scheme is a nation, the Strata Committee is the government. It is the responsibility of the Strata Committee to make decisions on behalf of the Owners Corporation in matters of repairs, by-law enforcement, minor renovation approvals, as well as gather information and present proposals for improvements and new/amended by-laws to the Owners Corporation for approval.
Strata "Management" - the Administrator
Your Strata Manager is a trained and qualified professional that assists the Owners Corporation and Strata Committee in the management of your scheme. The Strata Manager actions instructions from the Owners Corporation and Strata Committee, obtains quotes and issues work orders, proposes budgets for approval, issues levy notices, issues, runs and minutes meetings, and more. The Strata Manager is only allowed to make decisions as instructed by the Strata Committee/Owners Corporation, or as required by law.