Definitions provided by WordPress.
An Administrator is someone who has access to all the administrative features within a single site. Reserve this role for the site owner(s), site maintainer(s) and web developer(s).
An Editor is someone who can publish and manage posts including the posts of other users.
An Author is someone who can publish and manage their own posts.
A Contributor is someone who can write and manage their own posts but cannot publish them.
A Subscriber is someone who can only manage their profile.