Let's sort out some "Definitions":
A "schema" is actually a Database (as known from MySQL etc.), which contains tables, views, Indexes, Triggers, Stored Procedures and whatever else
Meaning: With the same Server you can have multiple "schemas" (Databases)
e.g. One schema called "SalesAndPurchases", another called "Accounting". Both have their own tables etc.
A User logs in to the one single server, and then per GRANTS it's decided if User A is allowed to take a peek at "Accounting", or if he gets "Err... no no...it's not your business how much the Boss earns"
I know this for a fact, since i HAVE such a scenario (though for IBM DB2)
in context of SQLite: SQLite is a single-file DBMS, meaning the usual case with SQLite is: 1 File, 1 Schema (=Database), which contains tables etc..
That schema is always called "main"
BUT: What you can do in SQLite is "attach" another Database-File.
Then you would have the scenario, which SF is alluding to: having 2 Schemas in SQLite (though i don't know, how that attached schema is called, since in its own file it's "main" again)