Most command line programs accept parameters like --help (originally from Unix) or /? (originally from Windows) that list their common options. latex (namely, pdftex, which is latex these days) is not an exception and recognizes --help. The same applies to other TeX engines like xetex or luatex.
On Unix, you can also type man pdftex etc. to read these programs' manual pages. MikTeX has them online; and TeX Live has the man pages in PDF format on your computer.
Modern TeX distributions (e.g. MiKTeX and TeX Live) have a texdoc command line tool. You can use
texdoc pdflatex
to get the document of pdflatex. Similarly, you can use texdoc --help or even texdoc texdoc to get help of the texdoc tool.
latex --helpfor a list of options and a short explanation.