Explain the stack in digital computers

The stack in digital computers is fundamentally a memory unit with an address register which can count only (after first value is loaded into it). A Stack Pointer (SP) is register where the address for stack is held as its value always points at top item in stack. The physical registers of a stack are always accessible for reading or writing unlike a stack of trays where tray itself may be taken out or inserted since it is content of word that is inserted or deleted.