http://y7yea4pmqqtznb33qiugvysyn2bob5v62e4pvoadoibrwkq3tsddjeyd.onion/ps/module/key-concepts-encryption
In the postcard illustration on the left (below), a sender writes: “HI! :-)” The sender addresses it to the message recipient. This message below on the left is unencrypted, and anyone passing the message along the way can read it.