If you got to the folder list screen by using the L command, then you have a few different options for manipulating your folders and selecting a folder. The two options ``view folder'' and ``folder index'' are similar in function (they both get you to a FOLDER INDEX screen) but operate on different folders.
``Folder index'' is something of an escape option; Pine keeps the same current folder as it had before you saw this folder list and simply displays that current folder. ``view folder'' is more of an ``open and view'' function, in that it makes the currently highlighted folder to the current folder, closes the previous folder and then displays the index of the new current folder.