Victims receive texts or emails purporting to be from Royal Mail claiming a package requires a small payment to be delivered. (along with other similar narratives)
Clicking on the link and providing your details leads to your money and/or identity being stolen.
Scammers send hundreds of thousands of these messages every day. Someone, somewhere, will receive one of these on the very day that they were expecting a parcel. The chances of a hit by the scammers is therefore extremely high. One moment of dropping your guard and clicking on a link is enough to make their day.
If you do click through accidentally then as well as compromising your device, the website may ask you for e.g. your date of birth to verify who you are before proceeding – having given up that piece of information to them they are then one step closer to your full identity.
There is a list of examples of some very convincing scam messages on the Royal Mail website – please make yourself familiar with these: https://www.royalmail.com/help/scam-examples