Starting SurrealDB with File: Option - Which One?

[PackMeister]

I wish surrealdb to persist its data in local files but there are a number of options.

I understand the memory option uses RAM only and so all data is lost upon shutdown or restart.

So best option appear to be either file:// or file:

However I can't locate any documentation explaining the difference and where/why I'd use one or the other.