Unidentified urine infection, but is it an std?

I went for a routine check up with my partner last week and we have been told that we have something taht is called unidentified urine infection, however i have been told that it is not an STD (my partners doctor said that it was an STD), but one of us infected anotehr. I am a bit confused as I am not sure what it is that we did have, and just wanted a bit mor information on it.