A/B testing importance

What is A/B testing in adwords ? How important it is ? and is it must for every campaign to have A/B testing ?

A/B testing is where you test two or more landing pages to see which landing page has better conversions…

It’s one of the best vehicles for determining what to scale. Our multivariate testing gets as specific as what colors convert better…

a/b testing is the discipline of testing interactions or engagements between two alternatives of a piece of digital content, usually a web page, email or piece of digital advertising. These techniques are useful to test a new piece of body copy or two equally strong pieces of creative.

From my point of view, a/b testing are needed in many cases but it depends on how relevant you considerate SEO for your own business