This web design is “adjusted” for a variety of devices (desktop, laptop, tablet, phone) and displayed correctly on them. Quite often this term is used in design development.
A service from Google to generate revenue by placing contextually relevant ads on your website. Quite often this term is used in contextual advertising.
Testing several variants of pages or blocks to determine the most effective one. Also, this term is used in advertising to determine the most effective ads or creatives. Quite often this term is used in contextual advertising.