When LaTeX creates your output file, it not only creates a PDF
file but also creates other associated files. The most common of these are
the log file, which has the extension .log, and
the auxiliary file, which has the extension .aux.
2.4 Auxiliary Files
The log file contains a transcript of the most recent LaTeX run. It lists all the files that have been loaded, including the class file and any packages that your document has used. There should also be the class or package version number and date, although this is dependent on the class or package author. If you ever want to ask for help, you need to say what version you are using.
(This is actually now out-of-date as the latest version at the time of writing this is version 3.11a dated 2012/07/05.)
Error messages, warnings and general information messages are also written to the log file as well as the document statistics. You can delete this log file if you like. It will be created again the next time you run LaTeX.
The auxiliary file contains all the information needed for cross-referencing (covered in §5.5. Cross-Referencing). This is needed to ensure all your cross-references are up-to-date. You can delete this file, but you will need at least two LaTeX runs to ensure your cross-references are correct the next time you create your output file.
TeXWorks also creates a file with the extension .synctex.gz. This file allows you to jump to and from the source code and the appropriate part of the output file. If you delete this file, you will have to run LaTeX again before you can use this function.
Other files that may be created include the table of contents file (.toc), the list of figures file (.lof) and the list of tables file (.lot). Some class files or packages create additional files. If your operating system hides file extensions, you might want to switch off this behaviour, if possible, to make it easier to distinguish between all the various files.
TeXWorks has a menu item File→Remove AUX Files that will remove the auxiliary files.
This book is also available as A4 PDF or 12.8cm x 9.6cm PDF or paperback (ISBN 978-1-909440-00-5).