Yes, you can get all you need for a definition by searching google. :-)

My definition (over-simplified) is that a binary (search) tree is a better data structure (non-linear) for searching really large amounts of information. It's much faster than, say, searching an array (linear data structure). In a binary tree, beginnning at the root node, each node has a pointer that can point to two other nodes - child nodes...ahhh it's a little involved to explain here, but not a difficult concept.

What is it that you are doing?? Do you have a book? Just curious.