I hope this help you:
Fields are the fields you want to be shown on your export file, so if you have streams like this:
you can export the entire data (fields: data), or specific data items (fields: data.temp), the 'at' field would be (fields: at), or combine all of them (fields: at, data.temp, device)
Query filter the streams before starting the export so (query: device: mydevice) exports streams filtered by mydevice.
Streams date range filters the streams by the 'at' field.
Sort sorts the streams ascending or descending by one or more fields (sort: at:desc)
Timezone timezone used to parse dates.