This "Affiliate Definition" clause provides a broad definition of an affiliate in relation to either party in the agreement. An affiliate includes:
1) Any entity that directly controls a party to the agreement. For example, a parent company that owns a majority stake in one of the parties.
2) Any entity that is indirectly controlled by a party to the agreement. For example, a subsidiary in the corporate group of one of the parties.
3) Any entity that is under common control with a party. For example, two subsidiaries owned by the same parent company.
The clause specifies that control means having the ability to direct how an entity operates and makes business decisions, whether through ownership (like owning a majority of voting stock), contract, or other means.
In summary, the purpose of this clause is to define affiliate relationships very broadly to include all variations of entities associated with and controlled by the parties. The history and rationale for such a broad definition is:
1) Limiting legal liability. Including affiliates under the agreement helps ensure the parties' related entities are also bound by responsibilities and obligations. Failure to include them could create loopholes.
2) Reflecting commercial realities. Large corporate groups comprise many associated entities, so the agreement needs to take this into account rather than treating each party as a separate standalone company.
3) Maximizing the scope. Especially in contracts where obligations, rights or benefits extend broadly across groups, the broadest possible definition of affiliates ensures all the intended entities are included, directly or indirectly. Narrower definitions could miss some parts of the corporate web.
4) Standard practice. A broad definition of affiliate has become fairly standard in commercial contracts, especially more complex agreements. It aims to be suitably comprehensive given how most large businesses actually operate through corporate groups and associated entities.
So in summary, this type of all-encompassing affiliate definition clause has become commonplace in contracts to match commercial practice, contain legal liability, and maximize the scope of the agreement across corporate groups and relationships. The exact wording may differ in some contracts but the principle remains the same.