What is the purpose of the Chilcot inquiry?

I'm a bit cynical when it comes to inquiries, esp this one. is it simply a case of proportioning blame against blair whilst not actually moving the whole thing to a criminal court? because lets face it realistically here that day will never happen and the whole inquiry is the usual appeasement for the public, or is it? comments ta except for how to spell inquiry I spell it my way lol.