TeXworks is free and open-source TeX editor, available for Windows, Linux and OS X, released under GPL v2.
It is a Qt-based graphical user interface to the TeX typesetting system and its LaTeX, ConTeXt, and XeTeX extensions. TeXworks is targeted at direct generation of PDF output. It has a built-in PDF viewer using the poppler library; the viewer has auto-refresh capability, and also features SyncTeX support (which allows the user to synchronize the PDF viewer position with the source, and vice versa with a single click). - Wikipedia