That is the standard TeX/LateX syntax.
You can check out LaTeX mathematic equation related document about those syntax.
There are some html which explain those [url=http://www.phy.ntnu.edu.tw/demolab/phpBB/viewforum.php?forum=21]syntax for equations displayed in EJS[/url]. However, it was all written in Chinese (my [url=http://www.phy.ntnu.edu.tw/demolab/phpBB/]Chinese version of physics discussion forum[/url].).

Actually, the equation displayed used in EJS was originally from [url=http://www.atp.ruhr-uni-bochum.de/VCLab/software/HotEqn/HotEqn.html]HotEqn - Equation Viewer
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You can check out their web site for more information.