The core of this paper is a discussion of how the physical signals of the nervous system acquire significance and meaning on the basis of relationships with each other and with the environment. Signal relations are discussed in terms of coherence (defined as lack of resistance), prediction, intentionality, inner reality and meaning. The original and most basic type of signal relation has the form of temporal correlations on coarser or finer time scales, and all other relations must ultimately be built up by the brain from this basis. Consequently, consciousness is the state of coherence of the brain in terms of signal relationships within it and with the environment. In this view, consciousness is of critical functional importance and far from a superfluous epiphenomenon. Understanding the mechanisms by which meaningful signal relationships are established in the brain is of great importance for the future of information technology.