An executive order can be issued by a mayor, a governor or the president. It is a legal directive and typically not questioned in a courtroom as to its authority.
In plain English, it is an act by the head of the executive branch of government without any legislative or judicial backup or approval. It is the closest you can get to dictatorship in a democratic form of government.
Biden has signed 42 executive actions since taking office. Here’s what each does
Source: Too many executive orders lead to abuse of power – Hartford Courant