Cialis is in a class of medications known as PDE-5 inhibitors, which are used to treat cases of male impotence. Elli Lilly and Icos are currently marketing Cialis in the UK and other EU countries and from 2003 in the USA as well.).
Cialis acts in the same way as Viagra, by blocking an enzyme called phosphodiesterase-5, or PDE-5. This helps the smooth muscles in the penis relax and widen, which allows for more blood to enter. As a result, you gain erections faster and easier with Cialis.

It is important to note that CIALIS does not work if there is no sexual stimulation. You and your partner will need to engage in foreplay, just as you would if you were not taking a medicine for erectile dysfunction. Ask your doctor if you have any questions about why CIALIS has been prescribed for you. Your doctor may have prescribed it for another reason. CIALIS is available only with a doctor’s prescription.

Be careful, there are many sites that will just take your money and either send you nothing or fake meds.

Here is how I decide if an on-line site is valid, it must have

1/ Guarantee on product quality (Country FDA approval)
2/ Guarantee on product delivery
3/ full selection of products
4/ Honest answers (FAQ’s, product descriptions)
5/ details on each product’s side effects (shows that they are not trying to sell you a product that might not be right for you)
6/ a real street address
7/ 800 number and on-line chat for questions
8/ a site that does not try and disguise itself as an information site when it is really just a sales site

and then I also want realistically low prices

LOW-COST-RX.COM is the site that I have used and trust