QUESTION: Is Dharana just "meditation" in an advanced state?
RESPONSE: Remember that "meditation" is an English word that is used in many different ways by different people. Most often, however, "meditation" is linked with "dhyana". It is extremely common in English speaking cultures to use the word "meditation" for any form of attention or concentration. Hence, for example, we have "meditation music" where the person is not at all concentrating in the strictest sense of the word, but is instead just listening to music (which is useful and pleasant, though not meditation as dharana).
There is a sequence:
Attention leads to concentration (dharana).
Concentration leads to meditation (dhyana).
Meditation (dhyana) leads to absorption (samadhi).
Like most arts or sciences, yoga has its own language, which is usually Sanskrit. The terms are more specific than the English words. English words are fine, once we understand the context of their use.
See also Yoga Sutras 3.1-3.3 - http://www.swamij.com/yoga-sutras-30103.htm
Attaining Yoga or Union:
Yoga or "Union" is attained by first training, balancing, and purifying each of the aspects of our being individually, and then systematically receding attention inward through those levels, expanding so as to experience the state of Union, Yoga, Samadhi, or Turiya.
