Link ads display a list of topics that are relevant to the content of your page. Link ads are closely targeted to the interests of your users. Because users directly interact with the topics, they may be more interested in the ads they eventually see.
AdSense publishers are paid for clicks on the ads that are linked from topics, not for clicks on the initial topics themselves. The ads on the linked page are pay-per-click Google ads similar to those shown in standard display ad units.
Link ads are responsive by default. They allow you to support a wide range of devices (i.e., computers, phones, tablets, etc.) by automatically adapting their size to fit your page layout. They're intended to work with sites built with responsive design, but will work on non-responsive sites too. Regardless of which device users use to visit your site, responsive link ads can help you provide a great ad experience.
To ensure that link ads continue to deliver a positive user experience, fixed-sized link ads are only available in the following ad sizes.
Note that certain fixed ad sizes might have less ad inventory available. Please take this into consideration when choosing a fixed ad size as it could have a negative impact on your earnings.