What does it mean to intercept all strangers' text messages?

Short messages sent by mobile phones without stored numbers cannot be received.

Interception of all strangers' short messages means that you can't receive short messages sent by numbers not stored in your mobile phone. Because interception is set, you can only receive short messages sent by numbers stored in your mobile phone after interception.

Stranger SMS refers to the SMS sending record between users and contacts who are not added to the address book.