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 nodes, as these operations only require updating a few pointers. In a singly linked list, the first node is known as 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 allocation, making them flexible in size and easier to manage when elements are frequently added or removed.