The difference between a test account and a live account is the ability to make a real transaction.

When your account is still in test mode, you are only able to use the development key for the testing transactions using API & not create a real transaction on your dashboard.

All transactions using dashboard test mode or API with using development key will never hit the bank system. Meanwhile, when your account is live, you will be able to use the production API keys & live mode dashboard. All transactions made in live API keys & live mode dashboard will hit the bank system.