What is Yoast?
Yoast SEO is a WordPress plugin that improves your website's rankings on search engines, by helping you optimize your site's content and keywords. A lot of what Yoast SEO does is automated, but still needs your input and some planning.
What is Yoast used for?
Yoast SEO is a WordPress plugin that helps your site perform better in search engines like Google. It also gives you the tools to bring your content to the highest standards of SEO and overall readability.
Is Yoast any good?
As a whole, Yoast is an awesome, powerful tool that does (at a guess) 70%ish of the stuff you need for SEO, even the advanced stuff. And it's free! So I'm not a Yoast hater by any means. But it's important to be aware of its limitations as well as its super powers.