What's the introduction about `/snmp.yml` of `snmp_exporter`?

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When I read this doc snmp_exporter:

there have brief introduction:

Volumes  
Mount your configuration at /snmp.yml.

Filesystem
/
├── etc
│   ├── group
│   └── passwd
├── snmp.yml
└── snmp_exporter

  1. I want to know /snmp.yml means the file in the host or in the docker?

  2. The Filesystem is the files in the docker?

  3. After I run it, I cannot docker attach ID to enter it.