The mh bundle is a series of packages designed to enhance the appearance of documents containing a lot of math. The main backbone is amsmath, so those unfamiliar with this required part of the LaTeX system will probably not find the packages very useful. Component parts of the bundle are:
empheq, flexisym, mathtools, mhsetup, breqn, mathstyle and
xfrac.

The empheq package is a visual markup extension of amsmath. Empheq allows sophisticated boxing and other marking of multi-line maths displays, and fixes problems with ntheorem package place end-of-theorem markers.

The mathtools package provides many useful tools for mathematical typesetting. It fixes various deficiencies of amsmath and standard LaTeX.

The mhsetup package defines various programming tools needed by both empheq and mathtools.

The breqn package makes more easy the business of preparing displayed equations in LaTeX, including permitting automatic line-breaking within displayed equations. (Breqn uses the mathstyle package to keep track of the current maths typesetting style, something that raw TeX hides from the programmer.)

The author is Morten Høgholm.