A Zap is a specific link between two services you've connected on Zapier. For example, New Salesforce Contacts to Add Mailchimp Subscriber would be an example of a Zap. If you wanted to move those same Salesforce contacts to an additional Mailchimp account or an additional Mailchimp list, that would be a second Zap. You can see all your Zaps from your Dashboard.
A Zap can be in one of three states: Draft, Off, or On.
Draft Zaps are incomplete, missing data that is necessary for them to be turned On. Click that Zap from the dashboard to enter that Zap and make the changes necessary to complete it.
Off Zaps are Zaps that can possibly be turned On, but are not currently checking for new data or performing tasks. To make a Off Zap On, click the On/Off switch on the right of that Zap in the dashboard. To edit the Zap, click anywhere else on that Zap.
On Zaps are checking for new data, and performing the action when the trigger is met. On Zaps only see data that has come across since the Zap was On. This means that while a Zap is Off, any data that comes in will not be recognized when the Zap is turned On again. To edit the Zap, click it from the dashboard.