SQLitePCL.raw is a Portable Class Library (PCL) for low-level (raw) access to SQLite. Packages named 'SQLitePCLRaw.provider.*' (like this one) are 'plugins' that allow SQLitePCLRaw.core to access the native SQLite library. This provider does DllImport of '__Internal', which is the mechanism used for pinvoke with a static library on iOS.
$ dotnet add package SQLitePCLRaw.provider.internalNo README available.