Skills
Each ability covers a broad range of capabilities and ways to interact with the world that are denoted as skills a creature can be proficient in. Each of these skills are further broken down into specific actions below, which may help guide how the skill can be used (and what rules are associated with that specific use). It should be noted that these uses are largely intended to be used as guides and do not embody every possible use of each and every skill. If a course of action doesn't fit under one of these skills, a DM may call for a general ability check (meaning no skill proficiency is added) or they may call for just a generic skill check.
Supplemental Skills
If the DM calls for an ability check that can use multiple skill or tool proficiencies, having proficiency or expertise two of them can further aid your roll. If a character has proficiency in both skills/toolkits, they may add a +2 bonus to the result of the d20 roll. If a character has expertise in both skills/toolkits, they may instead add a +5 bonus to the result of the d20 roll.
Trained vs Untrained Actions
Every action under each skill is denoted to be either "Trained" or "Untrained". Actions that are Untrained can be utilized by anyone, even if they do not have proficiency in the given skill. Trained actions can only be utilized if the character has proficiency in the skill. The actions listed on a skill page are not a cumulative list of every action the skill can be used for, but are instead guidelines for specific actions that normally will not change the ability score used.
Critical Successes and Failures
For the purpose of skill checks, critical successes and failures are not based on rolling a natural 1 or a natural 20. Instead, a critical failure results from a roll total that is 5 or more below the DC, and a critical success results from a roll total that is 5 or more above the DC. If your bonus is high enough, and the DC low enough, even a natural 1 can result in a critical success. Critically succeeding or failing on an ability check can result in additional benefits or detriments, depending on the check in question.
