Patch : This is the application of a corrective / evolutive patch on your CRM On Demand instance. The patch will first be applied on the Staging environment for you to test the stability and usability of your application. Then, a few weeks after, it will be applied to your Prod environment.
Standard Maintenance : This is a maintenance window that is used by Oracle to perform some routine work on your Oracle CRM On Demand application, this does not modify anything.
Refresh : This "refresh" line should appear only in the "Staging Maintenance Schedule" and refers to the copy of your production Configuration and Data to your staging environment. Very useful if you want to test something (maybe a new patch for instance) with your Production configuration and data.