The table is a list of lists. When you write data[[2]], you are asking for the 2nd part. At the top level, data is a list, so the 2nd part is the 2nd row, which is also a list. If you look up Part, you will see that giving it a list, as in {1,3,4}, asks for a list of those parts, which is the rows.

There are more complicated ways to use Part. data[[2,3]] asks for the element in the 3rd column of the 2nd row. data[[All,2]] asks for the 2nd element of All the rows.

Notice that the only thing that distinguishes rows from columns is convention. By convention the first index of a table or matrix designates a row, and the second a column. Following that convention, Mathematica displays a table that way.

hi David--

cool answer. Thanks! why does doing it this way (with the data[[{1, 3, 4}]] ) bring out the rows, as opposed for example instead of the columns? I am new to Mathematica but the simplicity and power of this language is incredible. Just trying to learn more!

-Joaquin