Perhaps you might want to read up about
dhyana meditation first in order to have some foundation upon which to ask questions.
First and foremost,
dhyana meditation is about developing concentration. Pure and simple. Most people coming to the practice for the first time experience something that has often been described as being "monkey mind" (a mind in motion, never settling down, constant movement going on), and are unable to bring the mind to rest upon only one object for observation.
What Gotama discovered (thinking back to a time when he was a child, attending a harvest festival with his father) was that he had been able to bring his mind to rest upon the simple inhalation and exhalation of the breath, which in turn produced a pleasant sensation that helped him to remain focused upon the breath.
[quote="MN 36.31-32"]31. "I considered: 'I recall that when my father the Sakyan was occupied, while I was sitting in the cool shade of a rose-apple tree, quite secluded from sensual pleasures, secluded from unwholesome states, I entered upon and abided in the first jhana, which is accompanied by applied and sustained thought, with rapture and pleasure born of seclusion.[389] Could that be the path to enlightenment?' Then, following on that memory, came the realization: 'That is the path to enlightenment.'
32. "I thought: 'Why am I afraid of that pleasure that has nothing to do with sensual pleasures and unwholesome states?' I thought: 'I am not afraid of that pleasure since it has nothing to do with sensual pleasures and unwholesome states.'[390]
Footnotes:
389. MA: During the Bodhisatta's boyhood as a prince, on one occasion his father led a ceremonial ploughing at a traditional festival of the Sakyans. The prince was brought to the festival and a place was prepared for him under a rose-apple tree. When his attendants left him to watch the ploughing ceremony, the prince, finding himself all alone, spontaneously sat up in the meditation posture and attained the first jhana through mindfulness of breathing.
390. This passage marks a change in the Bodhisatta's evaluation of pleasure; now it is no longer regarded as something to be feared and banished by the practice of austerities, but, when born of seclusion and detachment, is seen as a valuable accompaniment of the higher stages along the path to enlightenment. See MN 139.9 on the twofold division of pleasure.
From there he developed the remaining states (the eight levels of
dhyana) in his quest to attain awakening. Having developed those levels, he soon realized that awakening involves mindfulness, and that anything that hindered his ability to attain to a mindful state was incorrect practice. He also discovered that the first four
dhyanas were all that was necessary for him to attain to a mindful state. It is my impression based on experience that eventually he realized that
dhyana, then, became a practice to develop the ability to enter into
samadhi, from which he was then able to use as a spring board for contemplation. Contemplation (
vipassana or insight meditation), then, became the vehicle for his awakening.
Through the practice of contemplation, he was able to observe and categorize mental phenomena in an effort to better understand those phenomena as they related to the way he experienced life and living in a body. He observed that every phenomenon had three unvarying characteristics (impermanence, unsatisfactoriness, and without self nature), and that if he was able to become aware of the effect of these characteristics, that he could lessen the impact of
dukkha on his mind such that he let go of whatever clinging he had to the phenomenon. In letting go of this clinging, his mind was at ease.
This was his great discovery.
That said, once a practitioner begins to practice to reach these states of meditation, there are any number of experiences they can experience. The real question is: does it begin to help the practitioner develop concentration. (That is, above and beyond the extraordinariness of the experience itself and whatever pleasure or whatever one experienced.)
The state one should, in my opinion, shoot for is the stillness (non-motion of mind) and solidity (establishment of mind on an object of observation) of the fourth
dhyana, as this opens the door to the ability to attain
samadhi.
Samadhi is best defined as described below:
The Pāli noun samādhi is related to the verb samādahati, which means "to put together," "to join," "to combine," "to collect," and the past participle of the same verb, samāhita, meaning "collected," "composed." Thus, samādhi indicates "collecting" one's mind, and specifically in the context of sammāsamādhi, the mind composed in meditation. It is this composed mental unification which is termed singleness of mind (cittekaggatā). This meditative composure can be vast and expansive.
A mind in
samadhi has acquired integration or wholeness of composure, and is therefore able to observe and to obtain insight about whatever object it is holding in its grasp. Depending upon the practitioner, he may, at various stages of the practice, experience this as blissful or steady or established or any combination of these and more.