2.19 The stages of the attributes effecting the experienced world are the specialized and the unspecialized, the differentiated and the undifferentiated.
Sutra 2.19 is referring to the qualities of the Gunas. If you read my post "Losing Your Marbles" I talk about their nature. Other translations state that the Guans are either gross or subtle, manifested and unmanifested. These four stages of evolution are witnessed when the Yogi goes into meditation, following it's natural course over a long time period.
Gross, in the Yoga Sutras, refers to thoughts the lie on the surface of the mind. They have all their attachments associated with them. For instance, if you think of a doughnut, you may associate the taste, smell and the joy of eating it with the doughnut. So, specialized thoughts are completely unique to the individual perceiving them. Some people do not like doughnuts and have negative thoughts associated with them. Yoga refers to these people as weirdoes. How can you not like a doughnut?
The unspecialized, or subtle level of thought associated with an object in the mind do not have sense impressions attached to them. For example, you may see a picture of a far away place, but because you have not been to there, you can only associate with the image. I have never been to New York, but I have seen plenty of pictures. What I imagine it to be vs. going there are two different things
The next level is a little harder to describe. Differentiated means that the thoughts themselves are separated only by the fact that they exist as thoughts. That is why they can also be referred to as manifested. They exist simply because they are there. Have you experienced something and had a "gut feeling"about it? This is the deepest level of differentiation, It is so subtle, it operates outside our everyday awareness. With meditation, we learn that all objects are separated here.
Finally, there is undifferentiated or unmanifested. All objects exists with no attachment to them. When you take in sensory input of an object and there is no unconscious trigger, you have reached the "top of the ladder". The object is just there, existing on its own without the definition we put on it.