The Communication Grid is a planet-wide network on Cybertron active during the Golden Age before the Great War. Citizens across the planet can connect to it and converse with each other. It is also used to actively gather information, using receptors to see all and hear all. The Grid is constantly monitored by the Hall of Records to update the DataNet.
Orion Pax's monitor was hooked up to the Grid, recording the information and archiving it. Megatron was able to put out his philosophical broadcasts over the Grid, and it was also how Pax was able to send Megatronus a message to arrange a meeting. As Megatron's movement gathered momentum, the results of its bombings were often transmitted over the Grid, appearing on massive screens so that everyone could see.
When Omega Supreme came online after laying dormant for the war, he used the Grid to get himself up to speed on current events. The Grid was still online when the Autobots and Decepticons departed the ruined planet.