が , generally at the end of a sentence, (but sometimes starting a new one and followed by a comma) precedes an adversative idea , usually it's similar to けど/"but/though"
there are a few set expressions that use it for example, when you call someone using a phone "もしもし、たなかですが...".
Literally it's "but" but frequently the sentence isn't continued. It's up to the listener to figure out what the speaker is implying. It's used all the time to put some ambiguity at the end in keeping with the Japanese tendency to avoid strong pronouncements and give the other person opportunity respond agreeably (even if they disagree).
For example, instead of saying ピザをたべたいです (I want to eat pizza) you might say ピザをたべたいですが (I want to eat pizza but...).
In the first one, I may not want to eat pizza but I feel uncomfortable saying so because you unequivocally said that you want to eat it. Whereas in the latter one, the が at the end tells me you're probably open to other ideas. It implies that you are saying I want to eat pizza but we don't have to. This is all contextual so of course there are other interpretations. Like if you are in standing in front of a pizza shop and it's closed then I would take it to mean I want to eat pizza but they're closed.