Cows have four chambers in their stomach. The first is the rumen, the second the reticulum, the third the omasum, and the fourth the abomasum. The first stomach chamber is the "blanket" tripe, the second the "honeycomb" tripe and third is the "bible" or "book" tripe. The last chamber is rarely used because of its texture.
Honeycomb tripe is the most preferred for cooking.
Tripe has a gamey odor, which depends on what animal it comes from and what the animal last ate. The other ingredients cooked with tripe usually mask the odor.
Tripe is usually sold bleached and often is partially cooked. Unprocessed tripe needs to be cooked as long as 12 hours to make it tender enough to chew.