Applications are really small computer programs that carry out a specific functions. Obviously they have always been part of computer systems; without software a computer can't doa whole lot. So why the increased interest in apps, and what they achieve? Two reasons I think: software has often been very general in function (say a word processor) whereas an app tends to carry out one function and/or have one purpose as a piece of software. Secondly, apps are used on a wider range of hardware, particularly mobile devices. So, rather than sitting a desktop for a few hours a day using the programs (apps) people have potentially 24/7 access to the software which significantly broadens the types of function they might want from an app. It also means that apps can operate in real time and interact with other apps across a range of settings. I suspect software as a day to day utility (app) wasn't going to happen until easy to use highly accessible hardware become available.