A broad question, with equally broad answers. Computers are useful in many ways, from organizing complex data sets, storing large amounts of data (including WikiAnswer), interpreting said data (such as finding charts, plotting out data, trending and detrending data) displays of virtual worlds, communicating and associating with others, dealing with complex physics or engineering simulations... Really, the limit to the computer is more the data storage capacity and the speed of processing. Everything else is up to the user and programmer.