OS Technologies
Processors may be 32-bit or 64-bits.
Drivers and other software are often type specific - with a 32-bit processor we must use x86 software. 65-bit uses x64.
Note that 32-bit apps cannot run in 64-bit OSes, but 64-bit can run both.
On Windows, 32-bit applications will be installed in /Program Files (x86) while 64-bit ones will be in /Program Files.
ARM
Advanced RISC Machines are a different CPU architecture developed by Arm Ltd. They design the chip and other license the design to build it.
These CPUs have a simplified instruction set and as a result tend to be efficient and fast with less power and heat generation, often used for mobile and IoT. Note that these days we are starting to see lines blur between x64 and ARM OSes.
Hyper-threading
Hyper threading technology (HTT) allows one CPU to act as two CPUs. Note that this does not double the efficiency of the processor - it creates a 15 to 30% performance improvement.