This repository will be used by the mcoll application server to store all your database transactions. Since it's just a GitHub repository you can also access this data yourself.
The schema com.leftfetch.mcoll.schema.edn defines the structure of the database, which can be used to construct the datascript database.
The com.leftfetch.mcoll.tx.edn contains all the transactions that were applied to the database. If you want to reconstruct the database apply all the transactions in order to get to the current database state.