What are the ICAO PANS? What are their contents?
ICAO Procedures for Air Navigation Services (PANS) are documents approved by the ICAO counsel and recommended to states for worldwide application. As such they attempt to make air navigation services uniform across the world. 

There are five PANS:

Procedures for Air Navigation Services - Air Traffic Management (ICAO document 4444, a.k.a. PANS-ATM) 

Specifies the actual procedures to be used by air traffic service units in providing the various air traffic services to air traffic.



Procedures for Air Navigation Services - Aircraft Operations  (ICAO document 8168, a.k.a. PANS-OPS)

Lays down rules for designing instrument approach and departure procedures. Such procedures are used to allow aircraft to land and take off when instrument meteorological conditions (IMC) impose instrument flight rules (IFR).



Procedures for Air Navigation Services - Abbreviations and Codes  (ICAO document 8400, a.k.a. PANS-ABC)

Is a list of abbreviations and codes commonly used in aviation.



Procedures for Air Navigation Services - Aerodromes  (ICAO document 9981, a.k.a. PANS-ADR)

This details aerodrome licensing and Aerodrome Manuals 



Finally there is the PANS Training which details ISD (instructional Systems Deisgn and Systems Approach to Training (SAT) which enables criterion based and material dependent methodical learning