Registers
In plain terms
The fastest, smallest storage locations inside the CPU.
Going deeper
Registers hold the data and instructions the CPU is actively working on, offering the quickest possible access. They're the CPU's immediate scratch space.
Under the hood
Limited in number; compilers allocate them carefully, and register pressure forces spilling to memory.
Examples
CPU operations, assembly programming, accumulators, instruction execution.
Think of it like...
Like the few items held directly in your hands while working.