Google Cloud Messaging (GCS) is a messaging platform that allows users to send and receive messages across platforms, including Android and iOS devices, the web, and Gmail. GCS is free for users with a Google account.
However, GCS does have some limits. For example, messages sent to addresses outside of the US or Canada will cost $5 per message, and messages sent to addresses in China will cost $10 per message.
Additionally, GCS does not support video or audio messages.
Overall, GCS is a free and convenient messaging platform that is perfect for use with Google accounts.