{forward-inverse-search} is a technology for having synchronization between source and preview, e.g., being able to Ctrl-click (or similar) in the source and jump to the corresponding place in the preview of the document, and vice versa.

SyncTeX is a utility written by Jérôme Laurens which enables synchronization between your source document and the PDF output. Mostly this Feature is Editor/Viewer dependent, to see a list of Editors which support this Feature in Comparison of TeX editors under the Inverse Search column. If your editor/viewer supports it, then you can click in your source and jump to the equivalent place in the PDF or click in the PDF and it will jump to the appropriate place in your source document.

In TeXShop, for example, Command-click does the Navigation, in TexStudio right-click the source or PDF in built-in Viewer and select Go To PDF/Go To Source. Other editor/viewer pairs may implement the exact commands slightly differently.

The files that it creates store all of the synchronization data that make this magic possible. Gzipped versions of these files are created if you pass the --synctex=1 option to e.g. the pdflatex command (and other engines similarly); non-zipped versions can be created with --synctex=-1, although for a large document these files can be quite large, so the zipped ones are generally to be preferred. See

Usually this is part of the default setting for the compilation command within most TeX-aware editors.