What are Loki sources of getting the logs and how does it get the log information?

Hello,

I have just installed Loki and Grafana 6.4.

I need to know how does Loki get the log information and data that it has found for app, namespace, etc? And how does it get it?

I don’t see anything in docs that mention what sources Loki can get log information from for viewing,etc. or how it gets the log data.

Thanks

Freddie