Update README

Author: theandrew168

README.md

@@ -52,11 +52,13 @@ This key is intentionally absent from pg2s3's configuration in order to require
 | `age_public_key` | No        | Public key for backup encryption |
 
 ## Usage
-The pg2s3 command-line tool offers three commands:
+The pg2s3 command-line tool offers three mutually-exclusive actions:
 * `pg2s3 -backup` - Create a new backup and upload to S3
 * `pg2s3 -restore` - Download the latest backup from S3 and restore
 * `pg2s3 -prune` - Prune old backups from S3
 
+If none of these are provided, the pg2s3 will attempt to run in scheduled mode: sleeping until `backup_schedule` arrives and then performaing a backup + prune.
+
 ## Local Development
 To develop and test locally, containers for [PostgreSQL](https://www.postgresql.org/) and [MinIO](https://min.io/) must be running:
 ```