What is real time processing in information technology?

Real time processing technology captures and processes and responds to data as the events generating that data are happening in the real world. Unlike batch processing, real time processing deals with a continuous stream of inputs and has hard deadlines for completing tasks. 
A good way to understand the difference between real time and batch processing would be to think about data processing for airplanes. A scientist might study aircraft landings by having sensors collect data as a plane approaches the airport and lands, and then after the plane lands, process the data as a batch. For the scientist, there is no need to get results immediately. At the opposite extreme, imagine software that is used in autoland systems for aircraft in low visibility. The software has to process information concerning altitude in real time and correct the airplane's speed of descent in response to that information. A delay of a few seconds could result in the plane crashing.
Most forms of process control software, whether ones that help run complex machinery or ones that enable you to play video games, must operate in real time. Other types of software, such as banking applications or back office software packages, are usually handled by fast batch processing, which increases efficiency by grouping together large numbers of similar operations.