You will find 64-bit OS in most modern computers. It is always recommended to have a 64-bit OS for Linux as you can have good performance and security on it. If your system is running with an old 32-bit processer in that case only, you will need to install 32-bit OS. There might be a case when you are installing any software or an application that requires you to check the OS whether it is 32-bit or 64-bit? You can use your machine terminal and run the below command to verify it.
Architecture option is showing the x86_64 that means you are running with 64-bit CPU. If you find x86_32 that means you are running with 32 bit CPU.
CPU op-mode(s) option is showing 32-bit, 64-bit that means you are running with 64-bit Linux OS distribution. If you see only 32-bit that means you are running on 32-bit Linux OS distribution.