For the newbies they are just the strange lines forming a square but once known they are an effective part of the marketing strategy to easily grab the attention of the potential customers.
QR Stuff generates codes from the following Text, Website URL, Telephone Number, SMS Message, Email Address, Email Message, Contact Details (VCARD), Event (VCALENDAR)
Google Maps Location, Wifi Login (Android Only), Paypal Buy Now Link, Social Media , iTunes Link & YouTube Videos. You can also use their pay for service for other options eg t-shirts etc.