What does the expiration date of SMS mean? How to use it?

It's a text message sent to you by the other party. You can set 5 days, half a month, and one month. These are called expiration dates.

When you set a date to save yourself, for example, you set it to 5 days, after 5 days, the earliest message you received will be automatically deleted from your mobile phone.

SMS is valid and can be set on the mobile phone. Almost a few days. Hmm. How interesting