Shield wire?

[Simon-Pierre]

Hello, I'm redoing my oxygen sensor's wiring and in the wiring diagram there's a wire that connects directly to another one and there's a circle around the intersection ("T"). I checked the meaning of that symbol and all it says is "shield wire". What does it mean?

Blk wire: o2 sensor to ground, green wire: from Blk wire to computer

The symbol of the "shield wire" is where the green wire connects to the blk wire.

Thanks.
Simon