There are 3 "Actions" you can perform on one application or a group of applications from the Dashboard: Export, Halt, or Delete.
If you wish to Halt one or more processes from the dashboard (keep them in the system, but stop them progressing along steps to completion, you can select Halt from the Actions menu. Halting is a reversible action, although to have a process resume you must Resume it individually (there is no bulk Resume option. Learn more about Halting processes here.
Delete processes is useful if they were duplicates, spam, or test processes you created when you were working on a Workflow before it launched with the public. Be careful because deletion is not reversible. If you select Delete as a bulk action you'll be asked to enter the number of processes you want to delete as a precaution.