Simply put, computation is the many ways we simulate the world. This simulation could happen in the brain, in a crystal ball, in an electronic circuit, in a chemical reactor, or more. Originally, the purpose of this simulation is to predict the future (or at least the near future) for our advantages or survival. This goal is evident in the use of computation in meteorology, particle physics, biology etc. We want to know how the real world changes with given conditions and time, so we model the world with data structures in a computer, and run simulations on those “models”. To be practical, we have to ignore many apsects of the real word, so the models we have are only abstractions of it. The models must reflect accurately the aspects that we care about, without over-assumptions, that is, constraints or conditions that doesn’t really exist in the real world. Errors may be tolerable, but should be well-controlled. This is why computation is more and more important in sciences, because it lets us predict the future. In today’s sciences, it also lets us experiment with our “guesses” of how the universe was “built”. There are many other aspects of computation, for example as an information processing tool. Information is also part of the world, so we are actually using a computer for the same purpose: manipulating the world’s model.