What is register in computer ? What role do they play in computer?

Registers are high-speed memory which is located inside of CPU and serves to keep temporary data.
The role of registry in computer is-
(i) The ALU uses registers to hold data that is being processed.
(ii) It contains settings for low-level operating system components as well as the applications running on the platform.
(iii) The kernel, device drivers, services, user interface and third party applications all make use of the Registry.
(iv) The registry also provides a means to access counters for profiling system performance.
(v) The registry contains two basic elements-
a. Keys and
b. Values.