Plain text is what you need to quote, search, translate or feed a document into another tool. Only text that actually exists in the PDF can be extracted: a scanned document is a set of page images and contains no text until it has been through OCR. Columns, tables and footnotes come out in reading order as best the PDF allows, without their layout.
The defaults suit most files. Under Options you can choose which pages to convert and set or supply a password.
Only the text and its outline (headings, paragraphs, lists) are rebuilt. Tables, columns set side by side and images do not survive, and a scanned PDF, which holds pictures of pages rather than text, yields little or nothing because ToAny does not do OCR. A password-protected PDF needs its password, entered under Options; without it the file is refused.