Greenwich Mean Time (GMT) is a term originally referring to mean solar time at the Royal Observatory in Greenwich, London. It is commonly used in practice to refer to Coordinated Universal Time (UTC).
 

What does this mean in the forex market?
GMT provides a standard of time for the world when trading the forex market. GMT [...]

New York and London: 8:00 am – 12:00 noon EST
Sydney and Tokyo: 7:00 pm – 2:00 am EST
London and Tokyo: 3:00 am – 4:00am EST
 
Trading when market sessions overlap provides higher volume and volatility.
 
For example, trading EUR/USD, GBP/USD currency pairs would give good results between 8:00 am and 12:00 noon EST when two markets for [...]