CyanogenMod (pronounced sigh-AN-oh-jen-mod), is a customized, aftermarket firmware distribution for several Android devices (See above for supported devices & how to install CyanogenMod on said devices). Based on the Android Open Source Project, CyanogenMod is designed to increase performance and reliability over Android-based ROMs released by vendors and carriers such as Google, T-Mobile, HTC, etc. CyanogenMod also offers a variety of features & enhancements that are not currently found in these versions of Android.
While this build is heavily optimized, it is also capable of pushing your phone much harder. CyanogenMod and it’s team hold no responsibility to any damage caused to your phone, loss of earnings as a result of damaging your phone or anything else that is connected to the development of this rom.
For a list of devices officially supported by CyanogenMod, check out the official devices page. Such is the craze for CyanogenMod, that devices that aren’t officially supported, still manage to receive ports of the ROM courtesy of enthusiasts and developers. CyanogenMod offers the most barebone Android experience coupled with some very powerful tweaks. This whole package by now is not wholly developed by CyanogenMod developers alone, but is a collaborative effort between them and independent developers on sites like XDA-Developers.
Right now, CyanogenMod consists of two parallel and active major versions: CyanogenMod 7 is based on Android 2.3 (Gingerbread), and CyanogenMod 10 is based on Android 4.1 (JB); CM10-capable devices are being phased out of CM7, but since there’s a large amount of devices still on the market that aren’t capable of fully running Android 4.x, CyanogenMod 7 exists to support them. The variants of the firmware are split into categories, such as: Stable, Release Candidate, M-series and Nightlies. The Stable version, as suggested by the title, is the tried and tested variant of the firmware proven to be mostly bug free and suitable for daily use. The latest stable version is available for an assortment of the officially supported devices. A Release Candidate (RC) build may not be the final version, but a variant that has no fatal flaws or bugs, on the stabilization stages to become the final product that is the Stable variant. M-series releases behave similar to the RCs, but are considered ‘stable’ for our users. Lastly we have the Nightlies, which are as volatile as a firmware can get. These releases keep coming at an interval of a day or two and if you do end up trying one of these, do not be alarmed if the your device goes cuckoo on you. These ROMs are largely untested, and as advised by CyanogenMod, not meant for use for an average user. These releases, are meant to test untested waters that may or may not break your phone.