He discusses the change in his music, aiming for more depth, and rhythmic construction. He also discusses the idea of "displacement of phrases" which is most important to him and what he says is his basic conception of jazz structure. Evans illustrates what he means by displacement of phrases, against the melody, by playing, "All Of You" at the 4:30 mark.
Nobody can explain post-structure in jazz better than he. He does not just frame jazz as structure free. There is structure but, at the same time, there is freedom outside of that strict structure, where the music can move in and out. For Evans, the structure is not the melody or tune necessarily, it is more abstract that that. The structure is just "indicated" and not imposed. He explains what he means at the 19:00 minute mark. He suggests that the musician should have a complete picture of the basic structure. By structure he means it in an abstract sense. For example, the key of C to its dominate G 7th and back to the C and that is over a petal point. The song springs from there in a creative movement. He displays exactly what he means by that at the 20:00 mark and on. What a great teacher!
The explanation and example is awesome and as Marian mentions, there is a mystery there when you listen to it. There is so much in this exchange for the fan and for someone just interested in both the music and theory. Evans has an aphorism that it is better to practice one tune for 24 hours than 24 tunes in an hour! A good metaphor for many other things.