I just like listening to the traffic. Why do I hear 'cactus' sometimes referring to flight #?
This may also help...
Every airline in the world has a CALLSIGN...a nickname if you will.
Some are simple, American Airlines' callsign is "AMERICAN". United Airlines' callsign is "UNITED".
Some, not so simple. Atlantic Coast Airlines' callsign is "BLUERIDGE". And Virgin Americas' callsign is "REDWOOD".
Some make sense, some don't.
Here is a list of them all: http://www.faa.gov/air_traffic/publications/atpubs/CNT/3-3.htm
Chapter One sorts by company name first.
Chapter Two lists by callsign first, so if you hear one you don't know, you can look it up!
Chapter Three is by three letter designator first.