If you've been taken here after scanning a UK COVID venue QR code - your device offering to search for "UKC19TRACING" - then to make use of this QR code you'll need to load the UK NHS COVID19 app on your device so you can "check in" to the visited venue where the QR code is displayed. This is the app that is based on the purportedly privacy preserving Apple and Google Exposure Notification system so in theory your 'check-in' is anonymous and probably preferable to writing down your address/phone at said venue.
On an Apple iPhone/iPad when you scan these QR codes from the lock screen camera it will attempt to search for "UKC19TRACING" - which why you may have arrived here. Curiously this doesn't happen when the device is not locked and instead says "No usable Data found".
If you extract the content from one of these [big!] QR codes (with one of the many QR code scanning apps) it starts with "UKC19TRACING" and is then followed ":1:" and after that the main section is encoded in JSON Web Signature (JWS) [See RFC7515] format. Basically this consists of the following; after the "UKC19TRACING:1:" part there's three sequences of base64 separated by a dot("."), the second of which contains the venue name and postcode, and the other contain the signature and associated details - see here for more details.
If you're interested in creating a QR code for your venue see the the relevant gov.uk site.