All of these are probably better described in TypeScript. Check out type files for more!

loadConfig(Options?): Read and validate configuration. Fills in the config export.

config & default export: The single instance of loaded configuration, accessible after loadConfig.

ExportedConfig: Canonical type that configuration conforms to. Augmented in code generation.

Options | ConfigLoadingOptions: Options for loading configuration - see TypeScript types.

Options | SchemaLoadingOptions: Options for loading schemas - see TypeScript types.

loadValidatedConfig(Options?): Same as loadConfig, without changing config export.

loadUnvalidatedConfig(Options?): Same as loadValidatedConfig, but does not check schema.

loadSchema(Options?): Reads schema file.

loadMetaConfig(Options?): Reads meta file.

setLogLevel(LogLevel): Changes the internal logging level.

currentEnvironment(EnvironmentAliases?): Returns the current (canonical) environment, which is used for $env and others.

defaultAliases: Aliases that we apply by default. Currently, these are dev -> development and prod -> production.

ParsedValue (internal) : Structure of parsed config trees, which contains metadata like where each value came from.

ConfigSource (internal) : Abstract class for reading configuration.

FileSource (internal) : Reading configuration from a file.

FlexibleFileSource (internal) : Reading configuration from a variety of paths, looking for one that exists.

EnvironmentSource (internal) : Reading configuration from an environment variable.

LiteralSource (internal) : Reading configuration from a JavaScript object.

CombinedSource (internal) : Reading configuration from multiple sources that are merged.

FallbackSource (internal) : Reading configuration from the first of multiple sources that can be found.

FileType (internal) : Enum of supported file formats.

filePathAssumedType(string) (internal) : Converts a filepath to a FileType based on it's extension.

stringify(object, FileType) (internal) : Stringifies a raw object as a specific file format.

parseRawString(string, FileType) (internal) : Internal parsing function that knows all file types.