Owing to the around-the-clock nature of the forex market, it is divided into three trading sessions as different areas of the globe come online throughout the business day.
The middle session between the Asian and North American sessions is the European session. Tends to be the most active of the trading day due to the fact that it overlaps with the other two, and so has more active participants.
The European session centres around London, however, includes other major European centres including Germany and France. It typically trades between 7 am and 4 pm (GMT).