A Fibonacci heap is a type of data structure that supports a collection of priority queues. It allows for efficient operations such as merging heaps, decreasing keys, and deleting nodes. The structure consists of a collection of trees that follow the min-heap property, where the smallest element is always at the root. The main advantage of Fibonacci heaps is their amortized time complexity, which makes certain operations faster compared to other heap types. For example, the amortized time for inserting a new element is constant, while decreasing a key takes logarithmic time relative to the number of trees in the heap.