Prim is actually right only in one case. If QR code contains web site URL, it will do as Prim says. If QR code contains something else, it will trigger some other action on smartphone. For example, you can code any kind of free text into QR code or even vCard. If you code for example, contact card, it might also trigger adding that contact details in smartphone contact list
Check this to see what can you code into QR code
www.qrstuff.com/
You can see on that site that you can embed vCard but also check this notification 
VCARD information embedded in a QR Code will often result in a QR Code too dense for many mobile phones to read. To work around this, we recommend you choose the “link to download” option. This will embed a website link in the QR Code, and when someone scans the code, they will be taken to a web page that will prompt the user to download the VCARD VCF file (or, in the case of an iPhone user, to receive the VCF file by email.)