Colon cleansers for the most part act in the same way as laxatives. The goal is to remove the colonic content and toxins. The cleansers for the most part come in different forms, some gentler to the gut than laxatives.
There is no scientific evidence shown thus far to support any benefits of colon cleansing; the bowel itself is not dirty and cleans itself naturally without assistance. Some of these can cause electrolytes imbalance just like laxatives.