What does "A1278" mean in specifying a MacBook model? I need to replace a part in my MacBook 13", Aluminum, Late 2008 and I have found a piece that seems to match,  but I got confused by the code "A1278" in the description, which I have not seen anywhere in my machine's specifications.  It looks like it is associated with different models, not just with mine, and mostly with MacBook Pro.

What does "A1278" mean in a description of a MacBook model?  It seems to be referred to as model number, but it is shared by different models.  Would it mean that all models with this identifier are in some sense compatible?  Can some parts of one such model be used in another?
The model number can be found on the bottom side of your MacBook.



I have an app called "Mactracker" and it gives statistics for (allegedly) all of the various Mac hardware options. 

Here is some info on model number A1278:



Hopefully that helps.