Cybertronians would send messages to one another using their computer systems. Most are encrypted or secret.
Starscream sent Ratchet a message telling him that he had information regarding Optimus Prime's whereabouts and to come alone with medical supplies. Ratchet did but brought Bulkhead along since they couldn't trust him.
Starscream sends another message to Ratchet that he had information about Airachnid's Insecticon and to come with his medical supplies.
Dreadwing sent a message to the Autobots. Ratchet received it and informed the others that Dreadwing wants to meet with them.
The message system along with everything else in the former Autobot base was destroyed when the Decepticons blew it up.