I was scratching my head over the differences of Paranoid Android versus Cyanogenmod build or ROM. They both appear nearly the same. Everything are nearly identical with AOSP layout. This unlike, say MIUI which has heavy skinning over the most features.
Google provided a most interesting thread in Reddit. A Redditor has compiled a series of infographics highlighting the differences between the common builds. AvatarROM,PAC-Man, MIUI, SlimBean, OmniROM, Carbon, Paranoid Android, AOKP and CM 10.2
The aim was to see what the Xposed framework could offer against these builds. Please these builds or ROMs are mainly for use with Nexus line of phones. If you are using a legacy device like S2, some digging is required.
Note: ROM stands for Read Only Memory, this refers to hardware, a type of non-volatile memory that is the grandfather of the now common flash memory. Since we are talking about software here, so the nearest definition of software embedded into hardware is firmware. Another generic term that can be used is build, which I very much prefer.