GBS is a type of bacteria. It normally colonizes your particular body but when it gets out of control can cause an infection. So you do have a UTI caused by GBS if that makes any sense.
I had the same thing early on in pregnancy, took the course of antibiotics, which of course gave me a yeast infection. Once those were both treated I've been fine ever since.
At 35-37 weeks your OB would normally do a GBS swab vaginally/rectally to check and see if you have the bacteria present. Since you've tested positive for it in a UTI you won't need that done since you'll be considered GBS+ the remainder of the pregnancy, but you will need to be on antibiotics during labor/once your water breaks, as the bacteria can be harmful to the baby during delivery. The CDC website has some great information on GBS.