Dynamic memory allocation is a programming technique that allows a program to request and release memory during its execution. This is useful when the amount of memory needed is not known at compile time. Instead of using a fixed-size array, programmers can allocate memory as needed using functions like malloc in C or new in C++. When memory is allocated dynamically, it can be resized or freed when no longer needed, helping to optimize resource usage. However, it requires careful management to avoid issues like memory leaks, where allocated memory is not properly released, leading to wasted resources and potential program crashes.