A typeset operation triggered by the spinning wheel on the toolbar or Cmd-T triggers a typesetting chain that implements the complete sequence of calls to the underlying tools (typesetting or bibliography engines) such as pdfLaTeX, BibTeX, MakeIndex, etc that are required to typeset a document, compile its references and convert any PS or DVI files to PDF. Based on the choice of the underlying tool in typeset configuration pane (see above), Texpad calculates this sequence automatically.
The actual process of taking some text files with your LaTeX source and generating a PDF is handled by the underlying typesetting engines. A typesetting engine is an underlying tool or a set of tools that takes as its input a root latex document and produces a PDF. This underlying engine is often auto-sensed for you by Texpad. These include
pdfLaTeX: Used to generate most documents in PDF from LaTeX source.
LaTeX dvi2pdf: Used to generate a DVI and a PDF. Certain LaTeX packages may only work when typeset with this option – please consult the documentation provided with the package.
LaTeX dvips ps2pdf: Used to generate a DVI, a PS and a PDF. Certain LaTeX packages may only work when typeset with this option – please consult the documentation provided with the package.
XeLaTeX: Runs XeLaTeX to generate a PDF.
pLaTeX dvi2pdfmx: Runs pLaTeX to generate a PDF. This option is necessary to typeset documents written in Japanese.
LuaLaTeX: This is a version of pdfTeX with a Lua scripting engine embedded. It is modern and capable of typesetting a large class of LaTeX documents.
A typeset may additionally require compilation of bibliographies, indices, processing of R code (within your RNW files) and other formats within your LaTeX code. A bibliography engine is a tool that manages your reference files. It is entirely optional as LaTeX is perfectly capable of producing citations out of your references without the use of such an engine. Currently, Texpad supports three bibliography engine, BibTeX, Biber and BibTeX8. For compiling indicies, Texpad currently supports makeindex only, with xindy to follow in a future version. For processing RNW files, Texpad uses R with sweave or knitr related packages given as parameters.