Well, if you are unaware of the term QR Code, then here is the some useful info. QR Code is actually a 2D matrix barcode ( not similar but very much like the bar codes that we find on the commodities that we use everyday ). Each smartphone app has it very own QR Code which can be read and scanned only by QR code scanners.
Here is the step by step procedure to scan QR codes on iPhone:
STEP 1: Go to your iPhone Springboard and tap on the App Store to launch it.
STEP 2: There, tap on the Search button and type NeoReader. NeoReader is the actually the QR Code scanner for your iPhone which is a free app.
STEP 3: Once you find that free iPhone app, download it and install it.
STEP 4: Now launch the application, NeoReader that you have installed and tap on the button labelled as Settings. There, make the changes as per your need.
STEP 5: Whenever you need to scan a QR Code on your iPhone, simply launch that app and tap on Scan button at the bottom of Settings screen, position your camera such that it points the QR code and let it read it.
That is it! This is how you can scan QR codes on iPhone.