"Reviews" correspond to the number of, well, reviews that a member has submitted to LQ. You can review a piece of hardware, a book, or a distro. Please see the links on the upper right hand side of the page for more info.
The ratio you see reflects the number of original and followup reviews each member had. If you are the first person to submit a review on a given item, you get a point for an original review; if you add your review to an existing discussion, you get a point for a followup review. -- J.W.