According to ROG Learning Team (23 August 2002), The prime meridian is a geographical reference line that passes through the Royal Observatory, Greenwich, in London, England.
The line divides the between East and West and sits on longitude defined to be 0°. From that point parallelly towards East and west 360 meridian line are drawn representing longitude angles and the line meet at 180 degree which is known as Anti-Meridian
It was first established by Sir George Airy in 1851, and by 1884, over two-thirds of all ships and tonnage used it as the reference meridian on their charts and maps. In October of that year, at the behest of US President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference. This conference selected the meridian passing through Greenwich as the official prime meridian due to its popularity.
France However, abstained from the vote and their maps continued to use the Paris meridian for several decades. In the 18th century, London lexicographer Malachy Postlethwayt published his African maps showing the "Meridian of London" intersecting the Equator a few degrees west of the later meridian and Accra, Ghana.
Different Prime Meridians have been used through out the history by different civilizations including the Paris Meridian mentioned above. The prime meridian used to be located in the city the civilization is based on so, the Italians used Rome as Prime Meridian, Japan used Kyoto, which used to be capital of Japan back then and the Muslim world used Mecca, the holy city located in Saudi Arabia. However, During the age of exploration, instead of fighting with each other the colonial powers began to co-operate with each other. They felt that a common prime meridian is needed to make collaborations easier.
Prime Meridian and Greenwich Mean Time-
Greenwich Mean Time(GMT) is a synonym for Coordinated Universal Time (UTC). As we know that Greenwich seats on longitude 0°, Greenwich, several time zones has been created based on the Greenwich time that are defined by how much ahead or behind the time of the region is compared to GMT.
such as, Bangladesh time zone is called Bangladesh standard time (BST) and it is defined as, GMT+6 or UTC+6.