The main feature of PDF2XL is converting tables from PDF documents into Excel, which means you need to tell the application where in your documents there are tables that you want to convert.

To do that, you can mark certain areas on the document as Tables, and tell PDF2XL exactly how to format the rows and columns.

In addition to tables, there might sometimes be data in the document that you want to include in the conversion even though it's not in the form of a table. Perhaps you want to include page numbers, headers, or anything else that appears in one or more places but not as part of a table.
 To do that, you can mark certain areas on the document as Fields.

A field typically contains one item of data. You can choose how to include it in the conversion; e.g. Once, Every Page, on Every Line, or With Table (if more than one table exists on the page, you will be able to select which one to associate the field to).

Tables and fields are called "elements", and they are the building blocks of the Page Layouts.