They contrast with figurehead presidents, common in most parliamentary republics, in which the president serves symbolic, nonpolitical roles (and often is appointed to office by parliament) while the prime minister holds all relevant executive power.
To prevent the abuse of power, checks and balances are implemented through the legislative and judiciary bodies.
For example, in the United States one method is impeachment whereby the president can be held accountable if others deem their actions unconstitutional, with the most recent example being the impeachment trials of President Donald Trump.
In the corporate environment, the head of a company is the Chief Executive Officer (CEO), with the president being second in command.
In small businesses, the CEO and executive president are the same, whereas in larger companies the roles are carried out by two separate people.