United States Army Special Operations Forces – Afghanistan have been conducting operations since the fall of 2001. The SOF personnel have deployed from a number of U.S. special operations units (SEALs, Green Berets, MARSOC, etc.) and over time worked as part of several different SOF units in Afghanistan. Currently (mid-2016) almost all U.S. SOF units in Afghanistan fall under the command of the NATO Special Operations Component Command – Afghanistan / Special Operations Joint Task Force – Afghanistan. That is a long name for a military organization so most people just use the acronym of NSOCC-A / SOJTF-A. An even shortened version is NSOCC-A or SOJTF-A; depending on your nationality it seems.
NSOCC-A / SOJTF-A is under a United States commander – a Major General (two-star) position. The non-U.S. SOF units fall under the command of NSOCC-A. U.S. SOF come under SOJTF-A. The commander of SOJTF-A is also the commander of NSOCC-A; so he is dual-hatted. He reports to the commander of the Resolute Support Mission – a U.S. four-star general.
The mission of Special Operations Forces – Afghanistan is to conduct “. . . Security Force Assistance and targeted Counter-Terrorism (CT) in Afghanistan to ensure the enduring relevance, proficiency, capability, and sustainability of the Afghan Special Security Force as a CT partner, and to deny safe haven to Al Qaeda and its affiliates and adherents.” 
The components of NSOCC-A / SOJTF-A include the Special Operations Task Force – Afghanistan (SOTF-A), a battalion-sized unit (usually U.S. Army Special Forces), Combined Joint Special Operations Aviation Component – Afghanistan (CJSOAC-A), General Command Police Special Units Special Operations Advisory Group (GCPSU SOAG), and a task force working the CT mission.
Special Operations Forces – Afghanistan are involved in the Train, Advise, and Assist (TAA) mission working with a number of Afghan SOF units. These include the Afghan National Army (ANA) Special Operations Kandaks , National Mission Units (NMU) of the Ministry of Interior, and the Afghan Air Force Special Mission Wing (SMW). U.S. SOF is also heavily involved in the advisory effort for the Afghan Local Police (ALP) – a village-focused security program sponsored by the Afghan Ministry of Interior.
In addition, there are a number of advisory teams working with the Ministry of Defense (MoD) and Ministry of Interior (MoI) as well as at the institutional level to improve the ability of the ministries and schoolhouses to support and sustain the Afghan SOF units of the army and police.
 Mission description from USSOCOM 2016 Fact Book, United States Special Operations Command, page 42.
 The Special Operations Kandaks (SOK) are battalion-sized units of 700-800 men. There are ten SOKs in the ANA. Typically the U.S. advisors are from one of the U.S. Army Special Forces groups.
Special Mission Wing (SMW) helicopter from ISAF Facebook, March 4, 2015.
Shoulder patch photo from International Security Assistance Force (ISAF) website, 2013.
NSOCC-A / SOJTF-A patch image from @NSOCC-A Twitter account.
Featured image courtesy of CNN