a Liver Flush is a very specific protocol that causues the gall bladder to flush large amounts of bile, and the liver to contract and expel stones and toxins. this should only be done every so often. some find they can do a flush once a week, others need longer in between flushes to recover.
a cleanse is a more gradual detox protocol that you engage in on a daily basis for up to several weeks at a time. a typical liver cleanse herbal forumula contains milk thistle, oregon grape root, dandelion root, burdock root and a few others. these should be taken on an empty stomach. taking them with some lemon juice and/or some oil like olive oil or flax oil will increase the efficacy.