The Main Characteristic of 32-Bit Systems is the ability to address up to 4GB of System Memory. When the 386 from Intel was released, the typical amount of RAM in a system was 16MB. 4GB seemed like a barrier that woulnd't be crossed for a very long time. However, for Enterprise Customers running Servers, 4GB is too small a number for use on demanding database, and high-power applications.
For this reason, 64-Bit systems have now begun to be used.