This document discusses different types of data structures. It defines data structures as representations of logical relationships between data elements. It describes primitive data structures like integers and floats that are directly supported by machine instructions, and non-primitive structures like arrays, stacks, queues, lists, graphs and trees that are derived from primitive structures. Stacks are introduced as a non-primitive linear data structure that operates in a last-in, first-out manner, with elements only added or removed from the top of the stack.