Sofia,
The data in the file evidently has nested data that comes in as a list.
let's make something up:
data = {{a1, {bxx, byy, bzz, buu, bvv}, {cxx, cyy, czz, cuu,
cvv}, d1} , b, c}
data[[1]] gives the first element in the list (ignoring the b and c elements (which also could have been lists)
{a1, {bxx, byy, bzz, buu, bvv}, {cxx, cyy, czz, cuu, cvv}, d1}
next
data[[1,2;;-2]]
gives the second item and all items up to the second to last item in the result above:
{{bxx, byy, bzz, buu, bvv}, {cxx, cyy, czz, cuu, cvv}}
and once again they take the second item and all items up to the second to last item:
I made a confusing typo in my first edit of this post --
When you have a span, the next part range applies to each of the elements in the span:
In[4]:= data[[1, 2 ;; -2, 2 ;; -2]]
Out[4]= {{byy, bzz, buu}, {cyy, czz, cuu}}
This is useful for matrix operations. For example, if you want to take one column of a matrix you can use data[[1,All]] to get every item in the matrix
I hope this helps.
Regards,
Neil