There are subtypes of constipation, including IBS with constipation, chronic idiopathic constipation, and normal transit constipation. The Turds explain the symptoms and characteristics of each subtype and emphasize the importance of differentiating between them for proper treatment. The hosts also mention the use of physiological testing, such as anorectal manometry and rectal balloon expulsion, to diagnose and determine the underlying cause of constipation. They highlight the need for targeted treatments based on the specific subtype of constipation.