# Meaning of “Macro packages”, “TeX engines” and “Distributions” of TeX

I was wondering what relations and differences are between "Macro packages", "TeX engines" and "Distributions" of TeX？

I saw these concepts when looking at the following table at the end of this wikipedia page:

I am not able to find their meanings, and wonder what they mean?

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Possible duplicates (when combined): TeX Distribution and Engine and The differences between TeX engines. Macro packages are just a collection of macros, packages up into a bundle. –  Werner Jul 10 '12 at 4:48
@Werner: Thanks! (1) What do you mean by “packages up into a bundle“？ (2) Is LaTex a (Marco) package of Tex? –  Tim Jul 10 '12 at 4:50
(1) Should have read "Packaged into a bundle". (2) Plain TeX itself contains macros, and could be considered the first level above the TeX engine. LaTeX is built on top of plain TeX. That is, LaTeX is a bunch of macros built as an additional interface between the user and plain TeX (see `latex.ltx`). –  Werner Jul 10 '12 at 5:16
@werner -- latex doesn't provide an interface to plain tex, and indeed, some of the things it does are explicitly not according to plain's view of the world. –  wasteofspace Jul 10 '12 at 9:04
@wasteofspace: depends on what you mean by "plain tex": if you mean "plain tex – the macro language", then yes, LaTeX does provide an interface. If you mean "plain tex – the format", then… well, LaTeX does use plain as a base for many things. –  morbusg Jul 10 '12 at 11:14

The list is slightly muddled, through category errors; the criterion for inclusion is obviously "there's a wikpedia page on this one".

However, http://www.tex.ac.uk/cgi-bin/texfaq2html?label=texthings covers a bunch of them (mostly engines and format macro packages), and other early answers in http://www.tex.ac.uk/cgi-bin/texfaq2html cover a lot of the rest.

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