The executive power, all of it, is vested in the President, with a duty to 'take Care that the Laws be faithfully executed.' Congress writes the laws; the roughly 2.2 million civilian employees of the executive branch carry them out under the President's direction.
Read the clause itself, verbatim and in plain language, in the in-app Constitution.
The President, through the departments and agencies
In practice the power runs through the departments and agencies: prosecutions by Justice, tax collection by Treasury, benefits by SSA, each acting under statutes Congress passed and funds Congress appropriated. Enforcement priorities, prosecutorial discretion, and supervision of officials are where the President's control shows, and where the fights over its limits happen.
Constitution Annotated, Article II
Terms to know: Take Care ClauseArticle II's instruction that the President 'take Care that the Laws be faithfully executed', both a duty and a font of executive power.Full definition in the glossary · removal powerThe President's contested authority to fire executive officers without Senate approval. Its reach over 'independent' agencies is an active constitutional battleground.Full definition in the glossary · CabinetThe President's senior advisory body: the Vice President and the heads of the 15 executive departments, plus officials the President elevates to cabinet rank.Full definition in the glossary