Stack is a data structure that only allows elements to be added and removed from one end, called the top. It has components like a top pointer variable, elements that hold data, and a maximum size. Stacks can be implemented as arrays or linked lists. The main operations on a stack are push, which adds an element to the top, and pop, which removes an element from the top. These operations work similarly in array and linked list implementations, by incrementing or decrementing the top pointer and adding or removing the top element.