In an A/B test, what are you testing?

A/B testing is a type of marketing experiment where you test two or more versions of assets against different segments of your audience over a set period of time.
A/B testing is a type of marketing experiment where you test up to ﬁve variations of a website asset against diﬀerent segments of your audience, continuously.
A/B testing is a type of marketing experiment where you surface a variation of an asset that embodies your brand.
A/B testing is a type of marketing experiment where you create two diﬀerent websites, featuring very diﬀerent brand voices.