The Signal messenger and protocol.

I keep reading on articles, even those from this year, that Signal has an offline communications ability.

The articles talk about "Signal Offline" as an app. But that seems the same as the main Signal app?

Additionally, is there some functionality in Signal that allows you to connect with nearby users in the event when WiFi and cellular networks are down (like via some sort of a mesh network approach or Bluetooth)?

Edit: Thanks for the information to those who replied.