[Zope] What use is BTrees ???

[Max M]

I am unshure on how BTrees works, but I suspect that they might be 
usefull in a project I am doing, so I thought I might ask here.

I have an object which hase a dict as an attribute, in which I store 
other objects. I know this is a relative expensive way to do it as 
everytime an object is added to the dict the full object will be stored 
in the ZODB.

As far as I understand, the BTree is like a dict.

So do I understand it right that if I use a BTree as a attribute instead 
of a dict, it will only store the elements that are added/changed in the 
ZODB but otherwise act as a dict?

I use integers as keys in the dict

regards Max M