There are 4 different markets and these form 4 different forex trading sessions. And this Different forex trading session is given below.

The Sydney session, the Tokyo session, the London session and the
New York session.
The forex trading beings with the Sydney session and ends
with the New York session.
The Forex Trading Session explained stepwise.
Even though the forex market trading hours are divided into 4 sessions,
each of these sessions does not experience the same amount of activity
taking place during these hours.
The Forex Trading Session explained very easily on my YouTube channel.
Major forex trading sessions experience peak activity or high liquidity.
The Asian session, London session, and New York session.

Another Major forex trading session is

Asian forex session (Tokyo)
In this session markets of countries like Australia, China, New Zealand
and Russia begins their trading sessions.
At the start of each week's market, participants begin their activities from this session. This session is considered to be in action from 11 p.m. to 8 a.m. GMT.
The Asian session is the third most active session contributing to around 16% of total forex volumes.
European forex session (London)
In this time period markets of major countries like the UK, Germany and
France begins its trading session. Trading hours of the European
session begin at 7 a.m. and end at 4 p.m GMT. There is an overlap in
timings of the Asian and European sessions. This overlap leads to a
spurt in the volume of trading orders.

This session is considered to be the most active forex trading session as
a lot of volatility is seen in this time period. This session contributes to
roughly 43% of the total daily volume.

North American forex session i.e. New York trading sessions (New York)
The New York trading session forex is dominated by the US as
New York is considered to be an important financial hub. This session
begins at 12 noon and ends at 8 p.m. GMT. This session is the second
most active forex trading session as it contributes to 17% of the daily
volumes.
The European and American sessions make up for 60% of the total daily
forex volume.
And hence the overlapping of these sessions is the most active time period and is quite volatile.
I always get a question of which session is best for trading?
Each Forex session volume has its own characteristics. You need to choose the best forex trading sessions for you and start trading.
Like in the Asian session the liquidity and volumes begin to rise up. The Asian session is relatively less volatile and also the liquidity is less compared to the other 2 sessions.
Currencies like the Japanese Yen, New Zealand Dollar, Australian Dollar, etc are highly traded and experience significant movement during these sessions.
The remaining currencies do not experience much movement.
So if you were to trade on currency pair involving the Japanese Yen, New Zealand Dollar, Australian Dollar then the Asian session can be crucial for you.