Executive Orders, technically, are only orders from the Executive (the President) to the rest of the branch. As in, they can only tell the rest of the Executive Branch what to do, not create laws. However, with how much Congress has delegated to Executive Agencies, there's a lot more overlap and gray area than there was 233 years ago.

For example, the CDC has the authority to mandate certain things in the name of public health, because Congress created the HHS (who oversees the CDC) with the express purpose of doing so. So an Executive Order directed at the CDC can, in a sense, give the President that power.