Source Code Two BONE IK?

Hello,

could someone pls describe how TWO BONE IK works, because i already looked inside the kismet math lib but i didnt know which source codeTWO BONE IK exactly use. Ive also tried some tutorials one youtube about IK but they where pretty complicated and I think the source code of TWO BONE IK is a easier.

p.s. Sorry for my bad english

/Engine/Source/Runtime/AnimationCore/Public/TwoBoneIK.h
/Engine/Source/Runtime/AnimationCore/Private/TwoBoneIK.cpp

Here is.