1. There are many differences that you might choose for this answer, but two fundamental differences are that each node in a B-tree may contain more than one entry (whereas a binary search tree has...

1. There are many differences that you might choose for this answer, but two fundamental differences are that each node in a B-tree may contain more than one entry (whereas a binary search tree has one entry per node), and the number of children for a non-leaf node in a Btree is exactly one more than the number of entries (whereas in a binary search tree, each node has at most two children).

When searching for an item in a binary search tree, the searcher must always choose between going left or right at each node. In a B-tree, the searcher must choose among more than just two possible children.