What is Two-Step Verification?
Two-Step Verification is a process that either rings a phone number or prompts a smartphone when you login to your email account on a new device (or a prior device after 30 days). If your password is ever stolen, an attacker would also need access to answer that call or prompt.
Enable Per-App Passwords
App passwords allow 2-Step Verification users to access their Google Accounts through apps such as Mail on an iPhone or Mac, or Outlook. A password will be created for you. There is no need to remember them.