In Data Sync a data source is referring to the system you are connecting to. i.e. the Source data source is the system where you are pulling your data from and the Target data source is the system where you wish to move the data to.
Data Sync works on the concept of a Data Comparison Engine where you compare data in a source Data Source to a Target Data Source. Data Sync then takes care of the operations required to make the target the same as the source.
This is achieved by reading the data from the source and target systems then reconciles the data by joining the data sets via the Key Column(s) defined in the schema map
NB: Data Sources are sometimes refereed to as providers or connectors.
You can mix and match connectors between your source data and target data. For example your Source Data may be a CSV file whilst your Target is a SQL Server Table.
Data Sync defines the Source as Data Source A and the Target as Data Source B and the default mode is to sync A to B i.e. Left to Right. This can be changed to run in the opposite direction. However only Data Source A (Source) can apply Dynamic Columns, Calculated Columns and a Filter. Therefore it is advised to only run your projects A to B or Left to Right.
Connectors/Providers are usually compiled into a single .NET assembly and the capabilities are discovered at runtime via .NET reflection. There are a number of connectors included with Data Sync, you can also create your own via the Connector SDK.