What do all these letters/numbers in early Samsung ROM file name mean?
These 2 firmware names are a good demonstration of (early) Samsung naming conventions.


I8160XXLL2 is the "PDA" designator, i.e. build number;
I8160QXXLL3 is the "CSC" designator, i.e. baseband version.


There can be multiple CSCs corresponding to a single PDA, released for different regions.

Inside the string:


I8160 is, obviously the model number;
XX is for country/region (XX itself means Europe or international);
LL2 are the release date and version (within same month): first L for year (L for 2012, M for 2013, etc.), second L for month (A for January, L for December, etc.), and 2 for the 2nd version.


Furthermore, you can pinpoint which exact region the firmware is for by using a part of the CSC: QXX/QXE designates the precise region within the one defined in PDA. Match these 3 digits with a list of firmwares (e.g. on SamMobile), and you will know what regions received such releases.