The purpose of the innovation is to bring virtual communication via WhatsApp as close to an in-person conversation as possible, so messages should not remain in the chat forever. The option is called "disappearing messages." When this feature is enabled, messages will disappear in seven days after sending.
"We're starting with 7 days because we think it offers peace of mind that conversations aren't permanent while remaining practical so you don't forget what you were chatting about. The shopping list or store address you received a few days ago will be there while you need it, and then disappear after you don't," says WhatsApp blog.
In a chat with two people, one of them will be able to enable the function, and in chats with many participants, administrators will control its work. The option will become available to all users within a month.
You can read more, including how to enable disappearing messages here.
Meanwhile, a similar function has long been implemented in Telegram in "secret chats," and its capabilities are much more comprehensive. For example, the self-destruct timer can be set from 1 second to 1 week. Besides, the user will receive a notification if the interlocutor takes a screenshot of the chat.