When it comes to email marketing, what do we mean by the term A/B testing?

A/B testing means you can split your contacts alphabetically
A/B testing means you send the same email twice to the same people
A/B testing means splitting your audience and sending each of them a different variation of your email
A/B testing means it is spell checked and proofed, prior to hitting send

The correct answer is:

A/B testing means splitting your audience and sending each of them a different variation of your email.