Explain the principle of operation and purpose of B-trees in data structures.

B-trees are balanced search trees used for efficient storage and retrieval of data, especially in systems with large volumes of information, such as databases and file systems.

Main features and purposes of B-trees:

• Each node can contain multiple keys and have multiple children, reducing the tree's height.
• The tree is always balanced: all leaves are on the same level.
• Provides fast search, insertion, and deletion of data in logarithmic time.
• Optimized for working with external memory (hard disks), as it minimizes the number of read/write operations.

Example of application: indexing in a database, where a B-tree allows quick record retrieval by key without the need for a full table scan.