•So Aye Wassup Everyone Read All Info About A/B Partitions To Understand Better About Them.

•A/B System Updates Use Two Sets Of Partitions Referred To As Slots (Normally Slot A And Slot B). The System Runs From The Current Slot While The Partitions In The Unused Slot Are Not Accessed By The Running System During Normal Operation. This Approach Makes Updates Fault Resistant By Keeping The Unused Slot As A Fallback 

 If An Error Occurs During Or Immediately After An Update, The System Can Rollback To The Old Slot And Continue To Have A Working System. To Achieve This Goal, No Partition Used By The Current Slot Should Be Updated As Part Of The OTA Update.

Busybox Allows You Or Programs To Perform Actions On Your Phone Using Linux (Copied From Unix) Commands. Android Is Basically A Specialized Linux OS With A Java Compatible (Dalvik) Machine For Running Programs. The Android kernel is a modified Version Of The Linux Kernel (That Is Why The Android Kernel Must Always Be Open Source). Busybox Gives Functionality To Your Phone That It Does Not Have Without It. Many Programs, Especially Root Programs Such As Titanium Backup, Require Busybox To Perform The Functions Of The Program. Without Busybox Installed Your Phone Is Much More Limited In What It Can Do.

Xposed is a framework for modules that can change the behavior of the system and apps without touching any APKs. That's great because it means that modules can work for different versions and even ROMs without any changes (as long as the original code was not changed too much). It's also easy to undo. As all changes are done in the memory, you just need to deactivate the module and reboot to get your original system back. There are many other advantages, but here is just one more: multiple modules can do changes to the same part of the system or app. With modified APKs, you have to choose one. No way to combine them, unless the author builds multiple APKs with different combinations.

So Aye Wassup Everyone 

Here's Some Information About SELinux 

SELinux Is An Extension For The Linux Kernel To Increase Security. Put Simply, There Are Rules As To Which Program (Or App) Is Allowed To Do What, And Attempts To Do More Than That Are Prohibited. For The Rules To Be Applied, SELinux Should Run As Enforcing. The Rules Do Not Apply In Permissive Mode. For Example, If You Want To Root Your Smartphone, SELinux Would Cause You Problems Because Of The Rules, Because Apps Even With Root Rights Are Only Allowed To Do What The Rules Allow.