For

For[var, list] ... End

For[var, list] ... End executes the script at ... once for each element in list. In each iteration var is defined as the next element in list.

Example in out
Executes the script at ... exactly 10 times. For[ii, Range[10]]
    ...
End
The sum of the elements in list computed. list:={1,3,5,7}
sum:=0
For[ii, list]
   sum := CalcPlus[sum, ii]
End		 list = {1,3,5,7}
sum = 16
The list must remain unchanged during the iterations. list:={1,3,5,7}
For[ii, list]
   list := Concat[list, ii] # This is an error!
End