Microsoft is discontinuing support for TLS 1.0 and 1.1. Version 1.2 will be the default standard as of October 31, 2018.
The TLS is used on the web browsers, Internet Explorer and Edge. It is used by many email programs including Office 365.
You may get by with the older version of TLS in some programs. Just be aware if something quits working in a Microsoft program as of 1 November, you should look to see if this option is causing it.