|A cryptocurrency is digital money. There are many cryptocurrencies, just like there are many currencies like the dollar, the euro, and the ruble.|
Each cryptocurrency runs on its own blockchain, because every currency needs its own record of transactions. Imagine I had one dollar and one euro, and I spend my dollar. The dollar blockchain records this transaction, identifies the new owner, and that I don’t have that dollar anymore. On the other hand, this transaction does not affect the blockchain for all the euros.
If you own one ZEN, this means there is a transaction recorded on the blockchain where you received one ZEN, or several transactions that show you received a total of one ZEN.