Article Spinner or Article Rewriter, as the name itself gives you an idea, is a rewriting tool or a paraphrasing tool that allows people to rewrite their content while saving significant amount of time. Many such article rewriter and article spinner tools are available over internet. Some article spinner tools are completely free, requiring no installation or fee while some article rewriter tools can ask you to sign up or pay.
Think of it this way: What do you have more chance of hitting, a distant, tiny target or the broad side of a barn? For the sake of search engine optimization, you want your website to be the broad side of barn. The more quality articles, or unique readable content, your website or blog offers to search engines (and therefore the general public) the more exposure your website will receive from major search engines.
Its guaranteed that this tool will make rewriting jobs a lot easier than before because you can finally take a rest and let the software do the job for you. This is a wonderful tool indeed, and rest assured that everything will be perfect as long as you only use this tool for the sake of rewriting articles and not for changing a content thats the same as the article that you need to write and not rewrite. Expect that you will be able to make things a lot unique for the rewrites that you do with the aid of this tool because you now know how big its database is.
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.