My version of what Postcrossing is all about.
I used to be an avid member of Bookcrossing, much less so nowadays, but that's another story. As well as leaving books for random passers-by to find, people send each other books through the post. Very frequently a postcard was enclosed with a message. From time to time a straightforward postcard exchange was organised.
Then one day, someone drew my attention to a short announcement saying that a project called Postcrossing had been set up, a postcard exchange. I joined.
That was over seven years and more than 1500 postcards ago.
The goal of this project is to allow people to receive postcards from all over the world. The main idea is that: if you send a postcard, you will receive one back from a random Postcrosser from somewhere in the world.
Why? Well, it takes all sorts. The communicators like to receive mail of any description and are penpallers as well - the message is as important as any picture. The artists love to create mail-art and often incredibly skilfully. Then there are the collectors of quantity, or of particular themes - horses, food and beverages, castles, countries - anything that takes your fancy. The majority, I would say, just like to see places around the world in countries they might not have the chance to visit in person.
Ultimately though, it's random. You have no idea what you're going find in your mail, and I think it's that which appeals to me most.