Thank you Tweety.
Ok, more or lees, I understand like work visible in hmi, but when I go to wincc I see values that no mark with this option, for example take a i/o field, i go to properties -> process->tag, to the right of tag, i have two buttons, i click in the left button, and i see more values that isn´t mark with "visible in hmi", also I don´t undertand the next sentences:
"Accessible from HMI"-> Shows whether HMI can access this tag during runtime.
What´s mean "Shows whether HMI can access this tag during runtime."?.