A processor or central processing unit (CPU), is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logic, controlling, and input/output (I/O) operations specified by the instructions.
The processor (CPU) architecture can be either 32-bit (x86), 64-bit (x64), or ARM.
If you have a 32-bit CPU, you will only be able to install a 32-bit Windows 10 on your PC.
If you have a 64-bit CPU, you will be able to install a 32-bit Windows 10 or 64-bit Windows 10 (recommended) on your PC.
This tutorial will help show you how to check if you have a 32-bit, 64-bit, or ARM based processor (CPU) architecture in Windows 10.