Imagine an alternate reality, in which Jimbo Wales had created Wikipedia, the free encyclopedia! This would be a different encyclopedia, because he decided to let every single person in the entire world comment on article talk pages, and give their own opinions about what should and what shouldn't be written, about which articles should be created or not! Anyone and everyone would help building the document which would contain the sum of all human knowledge!
In order to actually edit the articles, adding and removing content to and from the encyclopedia, some users were granted editorship status. Now, this wasn't supposed to be a big deal. Their job was merely to check whether there was consensus for a change, and then actually make the change. Not everyone could be an editor, obviously, or else the whole thing would turn into chaos.