Skills

Skill Checks

Whenever a creature attempts a skill check, the roll always consists of:
d20 + skill bonus + proficiency bonus + stat modifier + other bonuses.
Each point that your character has in a skill is giving you a +1 skill bonus to the roll. As soon as your character reaches the rank of Trainee in a skill, you can add your proficiency bonus to the roll. Each skill has a stat that is tied to it. Sometimes this stat can be exchanged for another (example intimidation checks might be made with strength or charisma rolls). In the very end bonuses from magic effects and items are added.

Between success and failure

To succeed on a skill check you need to meet or beat the Difficulty Class of the roll. If you fail your roll by an amount equal to your proficiency modifier after reaching the at least the rank of trainee, you still succeed on your roll, but with a downside. This partial success could be something like:

You tried to jump over a cliff but failed your roll slightly. You manage the jump, but not the landing and slip. You are now hanging on the cliff and need help to get up. While a fail would've let you fall, the partial success basically gave you a 2nd chance in changing the outcome.

You tried to craft an item, but with the partial success you accidentally broke a small part off it, made a dent or ruined one of the detailed features. This could either end in a reduction of the item's value or in a situation where you need to spend more time and maybe material to correct your failure.

Ranks

The higher the level of a character's skill, the more efficiently they can use them. Not only are they able to beat higher DCs easier, but also they can use some abilities that are bound to a certain minimum skill levels. For example a Trainee in medicine might only be able to treat rank 1 poison, while a apprentice could treat up to rank 2.
Skills come in 5 different tiers:

Tier	Title	Points spent	Additional bonus
Tier 0	Beginner	0 points
Tier 1	Trainee	1-4 points
Tier 2	Apprentice	5-9 points	Add your proficiency bonus to the roll
Tier 3	Journeymen	10-14 points
Tier 4	Expert	15-19 points
Tier 5	Master	20 points

Difficulty Class (DC)

Tier	DC	Rank	Description of rank knowledge
0	5	Beginner
1	10
2	15
3	20
4	25
5	30
6	35
7	40
8	45

https://docs.google.com/spreadsheets/d/1ea3lkhaOrKFWfme1DqEzOudqvasr6d1--MAyOsIO2aE/edit#gid=1210316934

Teaching Skills

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