These are QR Codes. They are codes that contain data, such as a link to a website or a mobile app. They might contain information such as an email address or phone number, which is why people are starting to put them on their business cards.

How do I read it?

You simply scan it with your mobile phone. This requires a camera, so you most likely need a smartphone to read it. I use a barcode scanner on my Droid to read them.

How do I make one?

Very easy. Go to a QR Code generator such as http://qrcode.kaywa.com/. There you type in your text and it creates it for you. Its free and takes a minute to create. There are many other QR Code generators if you do not like the one I recommended.