In general terms, Site Workflows perform in a similar way to List Workflows. The difference is in the scope in which they operate – while List Workflows run on items of the list on which they are deployed, Site Workflows don’t run on any specific entity; they just exist within the Site where they are deployed and perform their tasks.

• Start Site Workflow - here you will find how to run previously created Site Workflow
• Workflow Status - it has the same logic behind it as in List Workflows
• Launch Action - here you will find about differences between launch List Workflow Action and Site Workflow Action
• Action Launch Form - same as in List Workflow
• Site Workflow History - here you can check every step of workflow execution

There is no option to perform Bulk Action Launch for Site Workflows.