A dynamic array is a data structure that can change its size during program execution. Unlike static arrays, which have a fixed size, dynamic arrays can grow or shrink as needed, allowing for more flexible memory management. This is particularly useful in programming when the number of elements is not known in advance. Dynamic arrays typically use a contiguous block of memory and can be resized by allocating a new larger array and copying the existing elements to it. Common programming languages like Python, Java, and C++ provide built-in support for dynamic arrays, making them easier to implement and use.