Trust is the glue that holds societies together. It is impossible to have any sort of functioning society without trust.
So, what exactly do we mean by trust?
Essentially it means that we can depend upon something or someone.
In the first case we trust that when we flip the switch, the lights will come on. When we open the tap, the water will flow. When we turn the key, our car will start, and so on.
In the second case we trust that a person will do as they say and fulfil any obligations...