Blue messages and green messages

When you are sending messages to your friends through iMessage, you may notice there are blue messages and green ones. So, what’s the difference?

Blue messages mean that both you and the recipient have an iCloud account that has iMessage feature enabled. These messages are end-to-end encrypted and are transferred through the Internet. You could add special effects to this kind of messages.

Green messages are the normal ones and they usually go through your mobile network. These messages will not be encrypted.