AppiumLibrary is to test on smartphones with Android or iOS operating systems. It needs Appium server to interface with phone operating system and Robot Framework (through AppiumLibrary). AppiumLibrary includes parts of SeleniumLibrary, because they share the same technology (Selenium, webdriver).
SeleniumLibrary is to test on browsers (usually on computer like machines, but can also be used in smartphones’ browsers).
You should try to look for the Demo or examples of the libraries to understand their setup.