a simple way of explaining a covert operation is a secret mission

The FBI was carrying out a covert operation in Columbia.

We are all going on a covert operation.

There was covert opposition to the new leaders of the union.

A covert operation would be some sort of attack, that was executed in a way to conceal the identity of the aggressor. This is often referred to as Cove Ops or Covert ops by the Military.

Covert Action - 2002 Operation Rathole was released on:

USA: March 2003