/Could you please describe the different levels of samadhi?/
There are various minor samadhis, and among the minor samadhis, savikalpa samadhi happens to be the highest. Right after savikalpa comes nirvikalpa samadhi, but there is a great yawning gulf between savikalpa and nirvikalpa.
In savikalpa samadhi there are thoughts and ideas coming from various angles, but they do not affect you. While you are meditating, you remain unperturbed, and your inner being functions in a dynamic and confident manner. But when you are a little higher, when you have become one with the soul in nirvikalpa samadhi, there will be no ideas or thoughts at all. There nature's dance stops. There is no nature, only infinite peace and bliss. The Knower and the known have become one. Everything is tranquil. There you enjoy a supremely divine, all-pervading, self-amorous ecstasy. You become the object of enjoyment, you become the enjoyer and you become the enjoyment itself.
Sahaja samadhi is by far the highest type of samadhi. In this samadhi one is in the highest consciousness, but at the same time he is working in the gross physical world. One maintains the experience of nirvikalpa samadhi while simultaneously entering into earthly activities.
When we enter into nirvikalpa samadhi, the first thing we feel is that our heart is larger than the universe itself. Now we see the world around us, and the universe seems infinitely larger than we are. But this is because the world and the universe are now perceived by the limited mind. When we are in nirvikalpa samadhi, we see the universe like a tiny dot inside our vast heart.
In nirvikalpa samadhi there is infinite bliss. There is nothing in comparison to the quantity, not to speak of the quality, of that bliss.
The last thing we feel in nirvikalpa samadhi is power. All the power that all the occultists have put together is nothing compared with the power we have in nirvikalpa samadhi. But the power that we can take from samadhi to utilize on earth is infinitesimal compared with the entirety. All this I am expressing through the mind; it is not exact. But I cannot express with words more of the Truth that I have realized.
What is the difference between samadhi and God-realization?/
There is no comparison between samadhi and realization. Samadhi is a state of consciousness in which one can stay for a few hours or a few days. But once one has achieved realization, it lasts forever.
Savikalpa samadhi is an exalted and glowing state of consciousness, whereas realization is a conscious, natural and manifesting state of consciousness. When realization dawns, the seeker enjoys freedom from the human personality and human individuality. He is like a tiny drop of water which enters into the ocean. Once it enters, it becomes the ocean.