What does the national security advisor to the US president do?
As the name suggests the national security advisor briefs and advises the US president on matters of national security. The role is independent of the US State Department (which oversees foreign relations) and the US Department of Defense. It is intended that the role should be an independent policy advisor to the president. President Trump's administration faced criticisms in February 2017 that a parallel policy-making process had been established under White House advisors Steve Bannon and Steve Miller.