What is a project?
A project represents a codebase + database. An instance is subdomain + domain that is pointing to this project, e.g example1.mydomain.com. It is possible however to have several instances in one project... example1.mydomain.com example2.mydomain.com example3.mydomain.com Some of these instances may be owners/parents of other instances.
If you are reading this and you are being managed by a reseller/Blocworx representative then it is likely they have their own project of which your instance is on.