A trust level is a (subjective) degree of belief or confidence that a party has in (the truth of) X, where X is an arbitrary statement that can be true or false. For example, the degree of belief you have in that the president of the US makes the right decisions is the trust level associated with you (as a party), and the assertion "the president of the US makes the right decisions".trust levels are subjective judgements made by individual parties. Given the same exact circumstances, two parties will perceive different levels of trust based e.g.on their risk tolerance and history with trust issues. A statement would typically have as many trust levels associated with it as there are parties that have made such judgements. Note that parties may associate trust levels to their own judgements, including judgements about their trust levels themselves.
These trust level judgements are typically made at the unconscious level. They depend on circumstances, and information that parties find relevant for such an assessment, and are able to acquire. These judgements change over time, e.g. as new information becomes available that is relevant for such judgements, or that the party decides what information that wasn't relevant before must now also be taken into account.
Assessing the level of trust in X is distinct from deciding whether or not to actually trust X, i.e. decide that X is true, or that X can be relied on to be true. For the latter determination, the trust level of X would need to have exceeded some threshold, which typically depends on the consequences the party would like it to have. For example, a party may associate a trust level to the statement "Mr Salesmann will not sell me junk" In a situation where the party buys a pear from Mr Salesmann, the trust level would not need to be as high as in the situation where the party would buy a house from Mr Salesmann, in order for the party to trust that statement (to be true).