Basic question: Query (InfluxDB) meaning of FROM tag?

Hi,

when creating a new query in Grafana (DS: InfluxDB) most of the time there is “default” pre-selected in the query editor’s FROM clause.

What’s the purpose of this drop down box? I mean, I already do select the datasource on top of the query, so what the purpose of an additionally FROM clause?

Many of the Grafana demos in playground use values different than “default”, however I cannot figure out the source of those list items.

Thanks,
Michael