Init.d plays an important role in the world of Android development and*customization* It allows users to install scripts and mods to be run at boot—everything from battery tweaks to performance tweaks.*It essentially opens the door to a world of mods only possible through the Init.d process, which in turn is usually only*available*on custom kernels.

XDA Senior Member*Ryuinferno*has developed a script that allows the use of Init.d scripts on any rooted phone, without relying on a custom kernel. Term-init is simply a script that you run in terminal emulator, which will automate*the install process, as well as adding a few extra features thrown in by the developer. After this is done, Init.d support will be yours!

Ryuinferno has also created an alternate method of*implementation*by use of a flashable zip, known as Zip-init,*which gets installed in recovery in the usual way.

The only things required to use*Term-init or Zip-init are your rooted phone, Busybox, and a terminal emulator app.

Source: XDA Developers