Trust, as I will use the term today, is more than a simple belief in something or someone without supporting evidence. Trust is what develops when a group of people share an understanding that the rules for behaviour governing their system or society work well and make things better for everyone.
With trust, less effort is expended in keeping tabs on others, so systems can run more efficiently. With trust, people can develop confidence that others will, in fact, do what they say they will do. And over time, as trust builds, so does the credibility of those who are trustworthy.