The “Connection” defines how Syncmaven should connect to an external service, which typically involves a set of credentials required for this connection. Connections are defined in the connections folder of a Syncmaven project. Each connection is defined in a .yml or .yaml file and can reference environment variables through the ${env.VARNAME} syntax: 
package:
  type: docker
  image: syncmaven/facebook:latest
credentials:
  accessToken: ${env.FACEBOOK_ADS_ACCESS_TOKEN}
  accountId: ${env.FACEBOOK_ADS_ACCOUNT_ID}
Each file must specify two nodes: package, which defines which package should be used, and credentials, which contains the credentials. At this moment, Syncmaven supports only Docker packages on dockerhub. image indicates the Docker image to be used. Syncmaven talks to the Docker image through the Syncmaven Protocol.
It is important not to store credentials in the connection file for security reasons. Refer to them through ${env.VARIABLE} instead
The connection does not specify how the connected service should be used; it merely defines how Syncmaven should establish the connection. Connections are used in syncs to connect to destinations or enrichments.

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Connectors

Connector is a package that implements certain connection. At the moment, all connectors are packaged as Docker images and follow the Syncmaven Protocol.

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Destination Streams

Connector can implement destination, enrichment of both. Here we are talking about connectors that implement destination. Destination defines one or more Streams. Each stream is a logical unit of data that can be written to the destination, and represented by multiple rows sharing the same schema. In a way, stream is an equivalent of a table in a relational database. For example, a connection to Hubspot defines a stream called contacts that represents a list of contacts in Hubspot. It also might define a stream called companies that represents a list of companies in Hubspot. To see all streams available for the destination, run the following command: 
syncmaven streams -f project/connection/destination.yml
Why destination file is required, and I can’t just get streams from docker image?Streams depends on provided credentials. For example, different API keys might have access to different data in the same service.