How to Flash Android 5.1 in Moto E XT1022 I've update my Motorola Moto E with Android 5.0.2 in Soak Test. Here's my S/W version. . Somehow I was unable to got Android 5.1 update. thus I've decided to install it manually.
I've found Moto E 5.1 Stock ROM Here! But, my problem is how to follow these steps mentioned in website.  I mean what is Custom Recovery (TWRP), what is Factory Reset (System, Data, Cache, Dalvik)* and How to Flash ROM?. How to do this?.Thanks in advanced for any kind of suggestions, help or tutorial link etc...
A custom recovery is a replacement recovery software for your device. It basically has a backup feature and a system for installing unsigned updates (flashable zips).

Factory reset is a wipe of your user data and cache partitions. It does not affect other partitions, and can be done via stock recovery.

Flashing a ROM can be done in two ways: fastboot or some flash tool for stock ROMs, and for custom ones, by flashing a ROM zip through a custom recovery. For the installation of a custom ROM, not one of its updates, these partitions should be wiped: system, data, cache (app data cache), and dalvik cache (app code cache). Further information depends on the particular variant of the device you are on.