The Adobe website has great tutorials on multitrack sessions for Audition. One of my favorite tutorials is about clip volume matching, fading, and mixing because it teaches you how to smoothly transition between audio clips as well as how to combine multiple clips into one track. It also explains some of the different fade options:
No Fade- Deletes the fade or crossfade.
Fade In, Fade Out, or Crossfade- If clips overlap, lets you choose the fade type.
Symmetrical or Asymetrical (crossfades only)– Determines how the left and right fade curves interact when you drag them up and down. Symmetrical adjusts both fades identically, while asymetrical lets you adjust fades independently.
Linear or Cosine- Applies either an even, linear fade or an S-shaped fade that starts slowly, then rapidly changes amplitude, and ends slowly.
You can reach the tutorial at https://helpx.adobe.com/audition/using/clip-volume-matching-fading-mixing.html