log4ngx is a Typescript logging framework for Angular projects, based on concepts used in Log4j, Log4net, etc.
Loggers provide access to the methods for logging messages at the required Level. Each class - i.e. component, module or service - will usually define its own Logger which will identify that class within any messages logged via it.
The LogService is the factory with which you instantiate Loggers in each of the components, services, etc, in which you wish to log messages. Behind the scenes, it also orchestrates the dispatch of messages from the Loggers to the appropriate Appenders.
Appenders are responsible for sending log entries to the underlying target or service. Configuration will normally depend on the target/service, but all Appenders are configured with the layout format for messages logged to them.
The LogService is configured using an instance of the LogServiceConfig, typically created in your application's main module. The configuration defines the parameters used with each Appender and how each Appender relates to the various Loggers.
For more information about using and configuring log4ngx, see https://secondbounce.github.io/log4ngx/.