What is the Dharma?
Dharma' is what Buddhists call 'Buddhism,' the teaching of the Buddha. It means 'the way things actually are,' or 'truth.'

No fixed dogmas: 'whatever works' = Buddhism
Dharma is
whatever leads you towards freedom from emotional, energetic, perceptual and ideological restriction; freedom to live authentically, compassionately and wisely. Dharma is basically a box of tools - a vast number of practical methods for changing unhelpful response habits, distracted, dissipated and stagnant energy patterns, wrong perceptions, and unhelpful views.  

What is the Dharma Door?
It's you. Whatever that might turn out to be.
essential tool in unlocking the door which is you is mindfulness: awareness of the emotions, energies, perceptions and views that dominate how you live. For example, take a look at the material here.

Dharma is a Path of personal transformation
'The Eightfold Path' is about transforming your (1) views, (2) emotions, (3) communication, (4) behaviour, (5) livelihood, (6) energy, (7) mindfulness and (8) mental integration.  

  • (6), (7) & (8) mostly mature through using meditation techniques.
  • (3), (4) & (5) mature through ethics training with mindfulness.
  • (1) & (2) mature through acquiring wisdom through deep reflection.

Where does it go?
Awakening or Enlightenment is something anyone can make real if they turn their lives into an effort to develop the path. The Pali/Sanskrit word is Bodhi, Awakening. 'Buddha' comes from the same root and means the Awakened One.