Guide 1: Why crypto currency exists

Today:

Over the next 2,500 years (until today) how we traded items has continued to change. 
Paper money has replaced gold coins, and recently 'electronic money' has meant you can use Credit Cards and Internet Banking to buy items online. 

It's easier.

This means you can buy and trade almost any item without ever touching gold or silver coins, or needing a specific item the seller wants instead. 
Because all parties agree the paper or electronic money they receive will mean they can buy something else later, everyone is happy.

But there's a problem...