Shell corporation is a company without any sizable business activity. It generally does not hold any significant assets or business operations. A shell company does not have employees or generate revenues.
This is a type of company that is used to raise money and engage in a financial transaction. Though sometimes a shell company is used for money laundering, it is not illegal every time. Big players form a shell corporation as SPV (special purpose vehicle) to raise funds for projects or conduct hostile takeover.