Everybody agrees that redshift can be caused by relative velocity. The standard model is based on the assumption that redshift can only be caused by relative velocity. If so, the further away something is, the faster it is moving. This would mean that the clumps of matter in the Universe are all moving away from each other. The implication is that if we go back in time, all of the matter in the Universe was much more compact.
Note that this does not necessitate any sort of singularity, in which all of the matter existed at an infinitesimal point of infinite density and infinite temperature. The Big Bang could have simply been more dense, and hotter, than usual.
The BBT also does not require that all matter be created at that instant — the matter could have imploded on the centroid and then exploded. So while Creationists favor the BBT, the BBT doesn't prove or require creationism.
Universe is expanding.
