There are a lot of developers building Substreams and creating very useful transformations that can be reused by other people. Once a Substreams is developed, you can pack it into a Substreams package and share it with other people!
Essentially, a Substreams package is a ready-to-consume binary file, which contains all the necessary dependencies (manifest, modules, protobufs...). The standard file extension for a Substreams package is .spkg.
The Substreams Registry
In order to facilitate how developers share Substreams packages, the Substreams Registry (https://substreams.dev) was created. In the Registry, developers can discover and push Substreams.
For example, the ERC20 Balance Changes package is stored at the registry (https://substreams.dev/streamingfast/erc20-balance-changes/v1.1.0).
Using a Package
You can easily run a Substreams package by inputting the .spkg file in the CLI: