Hi Caio, it means you should damp the previous note to stop it ringing on beyond its intended length and causing a dissonance with the next note, something that can happen where you have a note on an open string. You can damp a note by touching the string with a thumb or finger, and these are usually indicated in the scores after a backslash (\) near the flower symbol. For instance, where you see \2 above the flower symbol, you touch the string with the second finger of the left hand, and where you see \i you use the index finger of the right hand.
In the second bar of this particular piece, for instance, you play the B on the second string, and then when you go to hold down the A on the third string with your second finger, you slope that finger slightly so that it also touches lightly against the second string and stops it ringing. Then you will only hear the A without any interference from the B.
Classical Guitar Forum.
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