A data structure is a way of organizing and storing data in a computer so that it can be accessed and modified efficiently. There are many different types of data structures, including arrays, linked lists, stacks, queues, trees, and graphs.

Data structures are classified into two categories: linear and non-linear. Linear data structures are those that are organized in a linear fashion, such as arrays and linked lists. Non-linear data structures are those that are not organized in a linear fashion, such as trees and graphs.

Data structures are used in various applications, including databases, computer networks, and operating systems. They are used to efficiently store and retrieve data, and to perform various operations on the data, such as searching, sorting, and inserting.