When we develop our blockchain products Nxt and Ardor we need to perform testing.
For this purpose, we keep another blockchain instance we call Testnet which is similar in functionality to the actual production blockchain also known as Mainnet but uses a worthless token.
When you connect to the testnet you see a Red message saying "You are connected to the TestNet!"
This means that any information you see in the wallet is just test data and does not represent any official amount.
Use this blockchain only for testing.
To turn on testnet add the following property to your nxt.properties file nxt.isTestnet=true and restart your node.
To connect to mainnet remove this property or set it to false.
Specifically, Ardor versions up to 2.0.8e were always connected to testnet.
Upgrade to the latest version of Ardor in order to connect to mainnet.