The Presidential Medal of Freedom is an award bestowed by the President of the United States and along with the comparable Congressional Gold Medal bestowed by an act of the United States Congress- the highest award in the United States.
It recognizes those individuals who have made "an especially meritorious contribution to the security or national interests of the United States, world peace, cultural or other significant public or private endeavors.
The award is not limited to citizens of the United States and while it is a civilian award, it can be awarded to personnel associated with the United States military with the military personnel often wearing it on their military uniforms.
It was established in 1963 and it replaced the Medal of Freedom that President Harry S. Truman had established in 1945.
In the NCIS episode, Kill Ari Part 1 (episode), before resigning from NCIS, Director Thomas Morrow approved NCIS Special Agent Leroy Jethro Gibbs's suggestion that NCIS Special Agent Caitlin Todd who had been killed in the line duty by double agent/terrorist Ari Haswari in the Season 2 finale episode, Twilight (episode) be given the Medal of Freedom.
When Gibbs arrived for Kate's funeral in Kill Ari Part 2 (episode), the coffin opened to reveal her wearing the Medal itself as Gibbs apologized for being late to her funeral.