HALO - High Altitude Low Opening
Method of parachute insertion for special forces personnel and equipment. Egress from the dropping platform at altitudes in excess of 30,000 ft have been undertaken, though it is usually practiced at half this height. High altitude exit allows for covert insertion beyond the range of shoulder-launched anti-aircraft missiles and small arms. Individuals likely to perform this technique - also known as Military Free Fall (MFF) - are:
HAHO - High Altitude High Opening
Another method of parachute insertion for SF, this time using a paraglider-esque parachute to travel long distances after leaving the aircraft. Not to be confused with a HAHA, which is a wall hidden in a ditch.
For in-depth analysis, simply ask the nearest walt for an hour long diatribe about the merits and drawbacks of HALO/HAHO methods.