What is the role and responsibility of the executive branch?

The executive branch of the federal government is tasked with carrying out laws and enforcing them as defined by Article II of the US Constitution. Once a law is passed by Congress, the executive branch must oversee that the law is implemented and followed. This branch of the government is headed by the President. The President appoints the heads of the various cabinets and other federal agencies so that they may offer advice and implement laws.
The President, as head of the executive branch, also has certain checks over the other branches. The President can veto a bill passed by Congress and can also appoint federal judges. Congress can then refuse to confirm appointments and override a veto.
The military is under the command of the executive branch. The President is the commander in chief of the military, and the President can appoint military commanders.
This branch also has the power to negotiate foreign treaties, although they must be approved by the Senate.
The various government agencies that are part of this branch vary greatly. They include everything from the Department of Interior and the Federal Bureau of Investigations to the Environmental Protection Agency and the national parks. Embassies and diplomatic missions also fall under the umbrella of the executive branch.
The president has the power to grant pardons and commute the sentence of anyone convicted of a federal crime.
https://www.whitehouse.gov/about-the-white-house/the-executive-branch/