'Master morality' is the moral code practiced by The Übermensch. This means basing you moral code on your duty to contribute to the greater good of society by practicing a greater degree of individuality, leadership or supervisory skills such as planning, teaching, training, creating and innovating.
"Slave morality" is seeing a greater value in conformity, contributing, cooperation and contributing to the greater good of society by serving as a part of a greater whole and taking pride in the achievement of the group rather than personal glory.

An example is perhaps seen on a building site when the architect provides the pattern, the site project manager coordinates the the various skill sets and acquisition of raw material and so forth all showing "master morality" while the work force cooperating with one another, integrating their skill to produce a single or multiple tangible results as a joint effort are practicing "slave morality"

Looked at in modern anthropological circumstances some have speculated that Master Morality is seen more in those with higher levels of Neanderthal DNA in their make up and slave morality is a feature of those with predominantly cro magnon ancestry. The two types complimenting one another for success sociologically.