03-16-2014, 10:08 AM
Now for the technical (as best I can): each post is stored in a row in a database (think of a row in an Excel or Numbers document). Each row has multiple columns that need to be filled in with values. In the post by bobtomay, this includes a post id, a user agent string, an ip, and a date (this goes for all people but I'll use his post with the error as an example). One of these columns has to have a value that no other row has which, according to the error, is the post id column. This makes sense - people can have the same IP, user agent and can post at exactly the same time but each post is unique so each row will have a unique post id. This is why the post id is a 'primary key.'
The error is quite simple: it's effectively saying that the post id for bobtomay's post is the same as another in the database. In other words, his post id is the same as someone else's. This throws an error since his post id has to be unique (otherwise, his post would overwrite someone else's).
Think of it this way - people in a country can share a birthday, a name, an address, etc. but no two people can share something like a passport number. In this error, bobtomay's post is sent to the database with the same "passport number" as someone else which throws an error.
In case anyone wanted to know.