Due to the nuances of the NBA schedule, and more importantly television ratings, certain days are stacked with games (generally Fridays) and other days are relatively light (generally Thursdays). On the stacked days, it is common to have to rest a player or two that is technically active because all of your active roster spots are already full. These games are simply wasted games. Maximizing the number of games your team plays on off days can have the effect of increasing the number of games scored for your team in a given week, without actually increasing the total number of games your team played. This is accomplished by decreasing the number of wasted games as a result of the NBA's scheduling system. Think of it simply as akin to a gain in efficiency.
A quality game is actually a relative term, and the number is somewhat arbitrary. For purposes of this primer, a quality game is a game that occurs on a day when ten teams or less have games (i.e. five games or less on any given day). However depending upon league settings and the desired scarcity of quality games, quality games could just as easily be defined as eight or 12 teams playing (or any other number for that matter). Ten teams represents a third of the NBA, which is a convenient frame of reference for the quality games analysis.