The 6th house, naturally ruled by Virgo, is the home of work, health, humble service in the world, and domestic pets. It also relates to military service, domestic help, health-related professions, and service businesses.
When current planets transit through your 6th house, you need to simplify and organize those areas your life so that you can be highly efficient.
The 6th house asks the question, "How can I be of service to the world without becoming a slave to it?" A Virgo 6th house cusp may be a nurse or a veterinarian, whereas a Gemini cusp may provide information or technical services.
The 6th house is a major focus when exploring health and healing (though of course you need to look at a wide variety of factors to understand health in a chart). In general, the sign on the 6th house cusp points toward weaknesses in your health. A person with Aquarius, Gemini, or Virgo in the sixth house may need to avoid overtaxing the nervous system. Scorpio 6th house people may need to pay attention to dental care, reproductive organs, and the elimination system.
In relationships, the 6th house represents the practical elements of day-to-day life. When the honeymoon part of a relationship settles down, look to this house to organize your life, accommodating your partner and your worldly work.