A PTR (Pointer) is a variable in programming that stores the memory address of another variable. Instead of holding a direct value, a pointer allows developers to reference and manipulate data stored in different locations in memory. This is particularly useful for dynamic memory allocation and data structures like linked lists and trees. Pointers are commonly used in languages like C, C++, and Rust. They enable efficient data management and can improve performance by allowing functions to modify variables without copying their values. However, improper use of pointers can lead to issues like memory leaks and segmentation faults.