If you visited Wordstreams website recently then you're definitely on their "remarketing" list which is why their ads will follow you throughout the internet.

It's the same with anyone who has remarketing setup in Adwords. It's a code they install on their websites and when anyone visits the site, they're on the list. They can create custom lists for people who've visited specific pages and create ads tailored for those people. This works great for ecommerce because they can create remarketing lists for people who've "abandoned" the checkout process and get them back to the site.

Remarketing only works on the "Display Network" and not in regular search. The display network would be what you're seeing in the screenshot, ads on other websites.