B-tree of order n is an order-n multiway tree in which each non-root node contains

between n-1 and 2n-1 elements.

1. A B-tree of order n is a balanced search tree where each node has a specific number of elements and children, depending on the order of the tree.

2. The root node of a B-tree can have between 1 and 2n-1 elements.

3. Any other non-root node in the B-tree must have between n-1 and 2n-1 elements.

4. Each non-root node in the B-tree also has one more child than it has elements. So, if a non-root node has k elements, it must have k+1 children.

5. The elements in each node of the B-tree are ordered, and they separate the values in its children. If a node has k elements a1, a2, ..., ak, and k+1 children b1, b2, ..., bk+1, then all elements in bi are less than ai for i=1,2,...,k, and all elements in bk+1 are greater than ak.

6. All leaves in the B-tree are at the same level, which means the tree is balanced. This property ensures that the time complexity for search, insert, and delete operations in the B-tree is logarithmic.