In forex, four major forex market exchanges are located in London, New York, Sydney, and Tokyo. Since they all are in different locations of the world, their hours of operation are also unique.
Therefore, not all hours of the day are equally best suited for trading.
When more than one of them is open at the same time, there will be a heightened trading atmosphere. This means that there will be a substantial fluctuation in currency pairs.
When there is an overlap of the hours of trading, that time is considered the best for trading. It results in higher price ranges, resulting in greater opportunities.