Do I need the import_extras line?
If you want to provide the most specific information about the MAME games when creating romlists to later use with rules to filter and/or better describe the games in layouts it needs to be done one of three ways in your emulator MAME.cfg file.
1. use the real/full MAME emulator (not the RetroArch core)
info_source listxml
2. (works with RetroArch) provide the files listed in the import_extras line to let Attractmode where they are located (something like)
import_extras .\extras\mame.xml;.\extras\catver.ini;.\extras\nplayers.ini
3. (works with RetroArch) scrape the info from thegamesdb.net
system Arcade
info_source thegamesdb.net
You can also not provide any of this information and you can generate a romlist that will be usable but show you raw file names instead of the actual arcade game names. They will also lack the proper meta data for the games such as number of players, genre, year made, manufacturer, etc.
If you want to learn more about MAME you should search the forum (there's a lot out there on this) or make another thread. At this point this has nothing to do with American Laser Games.