In reply to Ste Brom:
Parkruns are terrific - they're a great way of monitoring how you're progressing (or regressing), and a good way to get your Saturday morning off to a lively start. If you go regularly, you'll also meet like-minded people.
The barcode is an integral part of the timing system - you carry your barcode with you on the run, and it's scanned as you finish, to give a time. Run results are usually uploaded within a few hours and you can get your results via text.
Because you have to carry your barcode, it's a good idea to either carry it in a clear plastic bag or cover it with clear sticky tape, to keep it vaguely waterproof.