Tadalafil is the active ingredient in popular ED medications such as Cialis. It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors, which work by increasing blood flow to the penis, enabling men to achieve and maintain an erection during sexual stimulation. While Tadalafil is a highly effective treatment for ED, it's essential to obtain it from a trusted source to avoid counterfeit or substandard products that can potentially harm your health.