A Module (or Configuration Item) is a generic term to describe any one piece of configuration within Flow.
For instance a Module could refer to a DB Connection, a Web Definition, a Map, or an Action. The following is a list of specific configuration items that are all referred to as Modules when discussed generically.
When a module is exported from the configuration database it is generally referred to as a Template. When a module is exported all the dependant modules are also exported to the template. This template can then be imported into another configuration database and the original module is recreated exactly.
A collection of Templates are bundled together they are generally referred to as a Package. A package normally contains related templates that provide a starting point when working with a particular business application. For instance the SAP Package provides all the templates you need to quickly create integrations for SAP.
A Connector is a special package that contains pre built connections between Packages of different business applications. A connector package requires that the dependant packages are installed. A connector package is provided for the common business applications that we have integrated together, an example is a Dynamics CRM and Dynamics AX connector package which provides integrations between the Dynamics CRM Package and the Dynamics AX Package