On the Internet, a guest author is someone that writes a guest post. That is content written for another website.
And why would someone write content for other than his/her site? Guest authors write for similar blogs within their industry in order to attract traffic to their site and increase their credibility and awareness.
Almost always, guest posting offers mutual benefits for both the guest author and the website hosting the guest content.
Crediting guest authors for their contribution is absolutely a must. So it is important to have a tool that allows you to do that properly and hassle-free. Molongui Authorship allows you to easily credit them in the post without ever creating a user account for them. This is a very handy feature because often guest authors are not regular contributors.