Sorry! I'll try to explain it better!
So your question regarded RAM, RAM has to do with running applications, and carrying out tasks etc. The way a computer functions is all with a number system called binary, base two. Our number system (decimal = 1,2,3,4,5,6,8,9,10) is in base 10.
So the number 32, in "32-bit OS" refers to the longest binary sequence that a computer can use to calculate a "..process or task.." To save you the math, the longest 32 to bit binary number, in decimal is : 4,294,967,296.
That number is in bytes. So typical RAM today is measured in GB. So time for more math!
4,294,967,296 bytes = 4,294,967 KB = 4,295 MB = 4 GB (approx).
So the largest capacity for RAM in a 32 bit OS is 4 GB, the rest can't be used because the software can't count in that many digits!
Hope that helps