TBH I've only just gone to have a quick look... It appears to be an online version of the grammar/spelling checkers that you get in most WP offerings... Except that you get to pay $5 for the privilege...
It seems to check spelling, common word misuse, cliches/common phrases, active/passive voice and a couple of other things that are all part of the standard grammar engine for Word, OpenWriter & LibreWriter.
Don't really see the point...
K