Here's a brief overview of the items available on the File->Publish menu:
* Web: This generates a set of web pages with chunked content (e.g. one page per DITA topic), and a frameset with controls for TOC, index, etc. Suitable for uploading to a web server.
* Digital Media Publisher: generates a PTC-flavored self-contained online-help-style system, with TOC, index, bookmarking, an updating system, and other nice features. It is based on JSP, so it offers a high degree of customizability. This is the system used for the Help Center included with Arbortext Editor and other PTC products. Requires additional license.
* HTML Help: generates output files, including .hhc and .hhp files, suitable for compiling with Microsoft's HTML Help compiler into a .CHM only help file.
* EPUB: generates output files suitable for processing with Calibre or other EPub compiler into an Epub document. These documents can be read in various reader apps, including iBooks on iPad or iPhone devices.
* HTML File: generates a single monolithic HTML file containing all output from the document.
* PDF File: generates a PDF file, based on options set in the stylesheet and in the PDF configuration file. (There is no built-in distinction between "interactive PDF" and "hard-copy PDF"-interactive features like hyperlinks and bookmarks depend on your stylesheet and configuration file settings.)
* RTF File: generates an RTF file, suitable for import into Microsoft Word or other word processing software. Requires additional license.
* Using XSL: Not technically a "Styler" output, but allows you to apply an arbitrary XSLT stylesheet to your document to generate a wide variety of output possibilities.
Each of these outputs is described in the online help, including information on publishing features that may not be available for specific output formats.