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.
The method is very simple, if you have the know-how of computers and internet then using this tool should be no trouble for you. All you have to do is copy and paste your text or article in the text box, and then click on the button saying “Re-write Article”. If you would like to play a little with this article rewriter tool before you go for it then you can use one of the given samples and watch it do its thing.
Imo it is not possible for google to detect properly spun content, it is not worth computing power it requires. They can do this using ngrams for example, but it is uses a lot of queries. And for example article spinner I coded beats this algo, so google cant detect that the content is spun. Manual spinning is also good but it takes more than 30 minutes per article.