Open market operations are used to implement the monetary policy of the ECB. They follow well-defined procedures.
More on procedures:
The Eurosystem manages the liquidity situation in the market through open market operations.
See the section "Liquidity analysis"
Access to open market operations is available to eligible counterparties, subject to their fulfilment of certain operational access conditions.
More on eligible counterparties:
Assets eligible as collateral in liquidity-providing open market operations have to fulfil certain
See the section "Collateral"