In May 2016 the United States confirmed that there have, since late 2015, been two teams of American Special Forces troops stationed in Libya. Totaling 25 operators, the American commandos are split between the coastal cities of Misrata in the west and Benghazi in the east. Unofficially there have been American commandos in Libya since 2011. Initially all the United States would admit to was a few CIA operatives in Libya collecting intelligence.
But when the CIA sends people in into situations like this, each group (usually a pair) of CIA people are accompanied by 6-12 U.S. Army Special Forces, often wearing civilian clothes. The Special Forces usually have better local language and cultural knowledge skills than the CIA people (who are sometimes former/retired Special Forces) and operate more as equals than armed escorts. This kind of cooperation has been around since the CIA and Special Forces were both created, after World War II, from the same organization (the OSS, or Office of Strategic Services). The common origin created links that have remained strong ever since. It's useful for the army, giving the generals an edge when it comes to getting something out of the CIA. In addition to Special Forces troops there are also former American special operations troops working in Libya to provide security for diplomatic personnel or other American officials making visits for negotiations or to collect information,
The two Special Forces teams now in Libya are there to monitor the activity of ISIL (Islamic State in Iraq and the Levant). Most of the several thousand ISIL members in Libya are in the coastal city of Sirte, which is between Misrata and Benghazi. Local Libyan forces based on those two cities are advancing on Sirte and the American Special Forces could also act as ground controller for NATO air strikes.