Connectors form the core of Microsoft Flow. Connectors allow your workflows to span across different systems. This means that you can quickly build business processes that span across all your systems allowing you to further automate your work.
Microsoft has, as of August 2018, 213 connectors, most are available with the free version of Flow, and some only available with Flow Plan 1 and Flow Plan 2. These are known as Premium connectors.
Work less, do more – that’s the catch phrase of Microsoft’s latest automation and workflow engine called Microsoft Flow. Microsoft Flow is currently in preview phase and still has a few bugs to iron out, but if you are familiar with IFTTT (If This Then That) workflow engine then using flow should come naturally to you. Essentially there are connectors to various web services (e.g. Dropbox, OneDrive, Dynamics CRM, SharePoint and so forth), and you can even program your own connectors.