A few years ago, Jeppesen's Jim Terpstra wrote a series of NavData Chart articles AOPA Pilot magazine. Reprints are available here.
http://tinyurl.com/4seqg
The NavData Chart Clinic Reprints, beginning with February 2001 provides explanations of leg types and fix naming.
Additional engineering-level details are available in the ARINC 424 specs themselves. The latest draft version of 424 is available here.
http://www.arinc.com/aeec/draft_documents/424_d1s19.pdf
Appendix Five contains descriptions and illustrations of the various leg types.
Best,
Zeffy