The Meta Level of an item usually depicts its relative power to duplicate modules of different Tech levels. The higher the number, the better... although it doesn't take into account superior fitting statistics.
The Meta Level also depicts the success rate of an Invention job using the module... although you aren't allowed to use a module with a Meta Level higher than 4.
The Meta Level of Civilian, Basic, and Tech 1 modules are all 0. Named Modules have Meta Levels of 1 to 4 (Named Basic is always 0). Tech 2 modules generally have a Meta Level of 5. Faction and Storyline Modules have Meta Levels of 6 to 9. Officer Modules can be 10 or higher.