The importance of an aftermarket recovery is undeniable. These amazing tools make various tasks easy, and allow users to flash various modifications, as well as create Nandroid backups that save us when we get the bootloop blues. Recoveries are also needed to easily flash a ROM. Because of this, you can pretty much find one or more custom recovery for every device with a forum here.
The most popular recoveries around are ClockworkMod Recovery, PhilZ Recovery, and Team Win Recovery Project. TWRP was recently ported to NovaThor SoC Sony Xperias: P, U, Go and Sola. The user responsible for the porting is XDA Senior Member NoobCoder.
The recovery is distributed in a rather interesting way, as a script splits the boot.img, extracts the ramdisk, adds the recovery, re-packs the ramdisk, and creates a new boot.img. Because of this, it can be used with every kernel available. Of course, the recovery might be also used on locked bootloader devices, but that requires some skills and various modifications to system files.