basics for FPM in webdynpro abap

Hi Experts,

I am new to webdynpro know some basic concepts.

I want to learn the FPM. what exactly FPM and why need FPM.

what is ehp4,we have to install any patches for using eph4 or any version we have to isntall.I have ecc6.0.

I know package ABP_FPM_DEMO in that some application using FPM are there.But I ma not understaing taht can you please give me small hello world application from step by step how to configure,what is configuration and what is the use of FPM.

Thanks