A structure is a collection of variables within one variable. Structures can be termed as a variable that aggregates variables of different or similar types. The correlation of structures and pointers is very strong. A structure provides a very intuitive way to model user-defined entities (records, packet formats, image headers, etc.). This chapter explains the basics of structures and their use with pointers; it also explains how structures can be used to implement data structures like trees, linked lists, etc. in depth.