I have been using Kaspersky since 10 years and no doubt its the best antivirus in the market. The box comes with an installation cd & manual which includes the license key. Like the description says this product is for 3 PCs and the license is valid for 3 years for each pc.
Some things to note :
1. It comes with only one license key (which is valid for 3 PC). 2. The license period starts when you activate it on the first device.