cialis Online is a medicine used to treat erectile dysfunction (ED, also called impotence). It is also used to treat problems with urination caused by an enlarged prostate (benign prostatic hypertrophy or BPH). It is used to treat adult males.It is sometimes known by its generic name tadalafil, and sometimes known by its trade name, Cialis. There are also other brands of this medicine available.Cialis is part of a group of medicines called phosphodiesterase type 5 (PDE5) inhibitors. It works by helping to relax the blood vessels in the penis, allowing blood to flow more easily. If you have erectile dysfunction, this can make it easier to get an erection.