Resources (such as images and help files) that are embedded into the binary of the application itself and typically not available as files.
Embedded resources are resources such as images and help files that are embedded into the binary of the application itself. Such resources would normally not be available as files. There are methods available for loading resources from URLs or input streams in most languages.
Java
This is how an URL might be formed, that points to an embedded resource within a Jar on the run-time class-path of a Java based app.
URL url = this.getClass().getResource("/path/to/the.resource");
This is how an input stream reading from the embedded resource can be formed:
InputStream is = this.getClass().getResourceAsStream("/path/to/the.resource");
Several detailed tutorials and examples are cited here.