Hi
I think you talk about the Mosaic Form (also known as Moment Form).
This is a form developed in the 20th century in which there are a number of SHORT sections (just a few measures each, not necessarily the same number of measures each one). Every part is distinct. You can use a lot of techniques to make them different: texture, scales, quicker-faster, modes, density, etc... Once you have all the sections you compose the whole piece making a "puzzle" with your parts and combining them in different orders to make a continuum. So, you don't have the typical repetitions used in earlier times (ABA, ABAB, etc...). The effect you get is a sensation of "no beginning nor end", as if you could take the piece from any point.
I studied Stravinsky's Sympony for Wind instrument and he uses the Mosaic Form with the following parts and order of them:
I have written several pieces in Mosaic Form, for example (the scheme is in the score):