Sorry, because it is really a basic question about music theory, but I am not a native English speaker and I have tried to search on the web and answer my question, but I am not able to find it. I am a beginner and I am learning on my own with the basics.
What does the flat (bemol) at the beginning of the stave do? What does it tell us?
Sometimes there are multipe flats (bemol) at the beginning, or multiple sharps (diese).