Inflation is the cosmological theory that the universe experienced rapid expansionary growth in the first instants after the moment of creation in the big bang. This rapid initial expansion followed by a period in which expansion continued but at a much slower rate had the effect that the large scale structure of the universe is isotropic, which is to say that it is the same more or less wherever you look. This explains the uniformity of cosmic background radiation because it explains how regions of the universe that are now causally independent. In particular, it explains that all regions of space have their origin in the same point.
