Final answer:
Hailey used a QR code to access the website of the company offering a mascara promotion, which enabled her to receive a discount by scanning the code with her smartphone.
Step-by-step explanation:
Hailey used a QR code (Quick Response code) to access the website. A QR code is a square-shaped, black-and-white barcode that can be scanned using a smartphone camera to automatically redirect the user to a specific URL or webpage, in this case, a company's website with a promotional offer. This innovative technology enables quick and easy access to digital content just by pointing a smartphone camera at the QR code and following the prompt.