In contrast to the familiarity of creating text with, for example, MS Word or another WYSIWYG-based approach, with LaTeX the creation of a document is conceptually different. Besides an editor, we also need a TeX distribution, a TeX compiler, style sheets and various packages that allow us to define i.e. a table or formula.
Let’s talk about some terms from the world of TeX that are really uncommon for someone who has never heard of TeX. (A brief as well as adapted summary of the article “The levels of TeX” from TUG website.)
Distribution: ProTeX, MiKTeX, TeX Live, Mac TeX, etc. These are the large, coherent collections of TeX-related software to be downloaded and installed.
Front ends and editors: Emacs, vim, TeXStudio, LaTeXila, Kile, etc. These editors are what you use to create a document file. Some are devoted specifically to TeX (e.g. TeXStudio), others (e.g. Emacs) can be used to edit any sort of file. TeX documents are independent of any particular editor; the TeX typesetting program itself does not include an editor. It is a good idea to use an editor which has syntax highlighting for TeX.
Engines: TeX, pdfTeX, XeTeX, LuaTeX, etc. These are the executable binaries which implement different TeX variants. As an example, pdfTeX implements direct PDF output, along with a variety of programming and other extensions.
The BFH CI supports only pdftex (pdflatex) and newer engines.
Formats: LaTeX, plain TeX, OpTeX, etc. These are the TeX-based languages in which one actually writes documents. When someone says “TeX is giving me a mysterious error”, they usually mean a format.
Packages: siunit, srcartcl, bable, etc. These are add-ons to the basic TeX system, developed independently, providing additional typesetting features, fonts, documentation, etc. A package might or might not work with any given format and/or engine; for example, many are designed specifically for LaTeX, but there are plenty of others, too. The CTAN sites provide access to the vast majority of packages in the TeX world; CTAN is generally the source used by the distributions.