In some cases (for example the expression parser) the user is allowed to specify an item (matrix, function...) entering only its name.
In most of the cases that's enough because only one item has that name.
When instead there are more items with the same name, Matrex displays this dialog to let the user select the item exactly, with its name and package.
Clicking OK the selected item is returned.
Clicking the Cancel button the dialog is closed but nothing is returned.