I am a largely self-taught writer through trial and error. Terminology is not a strong suit of mine, and I am not sure if I have written loglines here or actually done a synopsis?

I would call that a logline, but a bit too long. Also one typo (should be "barmaid's"). How about: "Something lurks under the surface in this psychological thriller as the arrival of a notorious escaped outlaw sets a frontier town and its secretive barmaid on a collision course with the past." I am intrigued by this because you normally don't see women tending bars in Westerns!