Testing programs should split traffic automatically, sending a certain percentage to your control site and the remainder to your “B” version. Different tools also allow you to segment your audience based on their browser, desktop vs. mobile, and other important demographic differences.
A/B testing is the easiest and most common kind of CRO. It involves testing a current design or “control” experience (A) against a new design or experience (B). A/B tests focus mostly on discrete elements, hoping to isolate which individual changes improve key performance indicators and which do not. Winning ideas are often implemented, becoming the new “control” for future A/B tests.
A/B testing–and conversion rate optimization generally–is important because it allows sites to make better use of their traffic, understand their customers more deeply, and challenge their existing assumptions. A/B tests teach you not only what actually resonates with your customers but what gets them to finally make a purchase.