This is absolutely useless. It claims it rewrites English sentences, but it just offers words alternatives, which is only nouns. Also, most of those suggested alternatives are unable to use. If you see their maker's home page, Whitehat Box, you can see numerous people request the refund. It's far from western progressive software like Grammarly or sketch engine. They stole my money with the diceiptive advertisement.
Before WordAi even starts spinning, it reads the entire article to understand both "generally" what the article is about and the "specifics" as to what exactly happens in the article. This allows WordAi to create complicated paragraph and document level spins based on its deep understanding of the article. Because no other machine has this level of deep understanding, it makes your content look human written. It is even able to correctly write high quality titles by identifying what the article is talking about.
Quality readable content is key here. Google, for example, will recognize that people are leaving your site soon after arriving if they perceive that your site or blog is full of junk content. This is called "bounce rate." If your bounce rate is high, then people are quickly leaving your site. But for the sake of your business, to build your online reputation and brand, you want people to visit your site, stay for a while, and then keep revisiting over the long term.