A singly linked list is a data structure that consists of a sequence of elements called nodes. Each node contains two parts: the data it holds and a reference, or pointer, to the next node in the sequence. This allows for efficient insertion and deletion of elements, as you only need to update the pointers. In a singly linked list, the first node is called the head, while the last node points to null, indicating the end of the list. Unlike arrays, singly linked lists do not require contiguous memory, making them flexible in size and easier to manage when elements are frequently added or removed.