what is this symbol?

[sf]

I copied something from email into Word (to edit) and turned
on show/hide. I had a few words with something after them
that looks like a "degree" symbol, but I see the are called
a "nonbreaking space". What is that and why is it used?

TIA

 

[MWE]

It means that the two characters devided by the nonbreaking space will not
be brokken into different lines (Seen as one word).