Fluctuation
The rise or fall in exchange rate within a short-term period; may be slight or dramatic depending on market and other conditions.
FX market operates 24 hours a day, 5 days a week. The week begins at 10:00 p.m. GMT on Sunday afternoon and runs until 10:00 p.m. GMT on Friday.
There are four major trading sessions: the Sydney session, the Tokyo session, the London session, and, the New York session.
As a trader, it is very important to find the right time and session to trade the market that suits your trading style and strategy.
Since this market operates in multiple time zones, it can be accessed at nearly any time of the day. Moreover, It is important to note that the market does not behave and move the same during all these four sessions.

At times when markets overlap, the highest volume of trades takes place. There are two main overlapping sessions that the market tends to move wildly, one is the end of Tokyo trading sessions overlaps with the start of the London session and the other one is the second half of the London session with the first half of the New York session.
During these two overlapping sessions market volatility and movements tends to be higher as these are the busiest times during the trading day and that is due to the higher volume generated by the two open markets at the same time.
Some traders prefer to trade when the market is most active, as not all hours of the day are equally good for trading.
As discussed, when more than one of the four market sessions are open simultaneously, there will be a heightened trading atmosphere, higher volume, and volatility that creates a greater fluctuation in currency pairs.
This condition could bring opportunity for bigger profits but also could lead to bigger losses due to heightened risk associated with greater fluctuation.
Traders should pick the trading sessions that complement their trading style and strategy.
In the next section "Intermediate", we are going to discuss technical trading terms, that would help beginners to fully learn and understand them.