In email marketing, A/B split is a marketing test method where an e-mail subscriber list is split into two groups; every other name in the list is sent one e-mail message and vice versa. The open, response and conversion rates to each message are tracked.
A/B split testing is used outside of email marketing in the wider category of online marketing. For example, you might show website visitors different versions of the same pages to see what works best. When done correctly, A/B can help you increase your conversion rates, address problem pages and challenge your assumptions about how to optimize your site.