Wizards and Filters
Before importing a file using the Text Import Wizard, define a general format, called a wizard that can be used repeatedly to import any number of files of the same type. A wizard describes 1) the contents of each column of data, 2) whether the columns are fixed-width or are separated by delimiters, and 3) which rows to import.
A wizard is made up of one or more filters. Filters are sets of parameters that describe different groups of lines within the file to import. In many cases, a wizard will consist of a single filter. This is the case with uniform data files. In a uniform data file, all the data lines to be read are of the same format. Because of the consistency of format, a wizard needs only one filter to describe a uniform data file. When you define a wizard for importing a uniform data file, the wizard and the filter are one and the same.
Non-uniform data files, on the other hand, contain rows of various formats (different rows exhibit different formats) in a single data file. To accommodate multiple row-formats, a wizard must contain more than one filter. Specifically, a wizard needs one filter for each type of row-format to be accommodated. In the process of defining a wizard for importing a non-uniform data file, you define multiple filters that, taken together, constitute the wizard.