How is being an executive different from being a manager?

There is not a simple answer to this question, because the definitions of manager and executives vary.

Executives are responsible for the long term continuation of the organization (whatever organization they're in).  Managers are responsible for the short term continuation (operations) of the organization.  As such, executives deal much more with the chaos of factors external to the organization: customers, competition in the marketplace, geopolitics, the environment, society.  Managers deal much more with internal systems and processes.

Executives as leaders have to make decisions about where an organization is going to go.  Managers get it to go there.  A healthy organization has both effective executives and effective managers.