What is it
From the documentation:
Stitch is a cloud-first, open source platform for rapidly moving data. A simple, powerful ETL service, Stitch connects to all your data sources – from databases like MySQL and MongoDB, to SaaS applications like Salesforce and Zendesk – and replicates that data to a destination of your choosing.
When to use it
We are currently evaluating Stitch for extracting data from Salesforce and loading into BigQuery.