Update README.md

Author: jeffgillan

README.md

@@ -173,6 +173,9 @@ The general directory structure on `stac-api` vm is:
 
 ## Run stac-fastapi with Docker-compose
 
+Within the directory `stac-fastapi`, the file `docker-compose.yml` is the config file to orchestrate the launching of 3 containers. These containers run the API. 
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+
 The `stac-fastapi` Docker-Compose will start up multiple containers, including a database which relies on the sample data.
 
 Note: the GitHub repository for `stac-fastapi` expects containers from GitHub Container Registry, not from DockerHub - update the `docker-compose.yml` to use the specific containers and tag version