You are correct that an enema does not involve suppositories...an enema is the introduction of a liquid...water, coffee, aloe vera juice, wheatgrass, etc....into the colon via the anus. There are basically two types of enemas...cleansing enemas and retention enemas. A cleansing enema uses water or a water solution in a sizeable quantity so that peristalsis is stimulated and the colon begins emptying its contents. A retention enema...coffee, wheatgrass, etc....uses a smaller quantity of liquid and it is held in the colon for a period of time and then expelled. A retention enema is more successful if performed following a cleansing enema...easier to retain and better absorption of the therapeutic properties of the liquid used.
Salt flushes are sometimes referred to as oral enemas...the salt solution is taken by mouth.
Go to enemabag.com and you can learn more than you probably ever wanted to know about enemas...click on Articles!
As for suppositories...there are many different kinds used for various purposes. Those that introduce a laxative pose the same problems as an oral laxative and should be avoided. Suppositories can also be used to soothe and heal inflammed tissue, to introduce antifungals, etc. What kind of suppostitory are you referring to and what are you using it for?