The main difference between SaaS and On-Premises lies in how the software is deployed and managed. SaaS (Software as a Service) means that the application is hosted and maintained by CKSource, and users access it via the cloud. On-Premises, on the other hand, is installed and managed on your own servers, requiring you to handle the infrastructure and maintenance.
For more details, please see the SaaS vs. On-Premises guide.