In simple term, a 'bit' is referring to the amount of data that the CPU can process at any time. A32-bit system usually means that the CPU can process32-bit of data at a time. Similarly, a64-bit CPU will be able to process64-bit of data, which is double that of a32-bit system. Since the64-bit CPU can handle more data at any time, it can theoretically allow you to load larger programs, bigger files, run applications faster and increase the performance of your computer. The latest CPU in the market now are mostly64-bit, and can handle both32-bit and64-bit instructions.
Other than the amount of data that the it can process, the amount of maximum RAM supported is also different for a32-bit and64 bit system.. A32-bit processors can only access a maximum of4 gigabytes (GB) of RAM memory while a64-bit system can support up to1 terabytes (1000GB) of memory.. Even if your motherboard supports up to8GB RAM, your32-bit OS can only recognize up to4GB, which means that the remaining4GB are useless.