Your training represents your progression in an area of specialization, granting you bonuses to rolls and features to equipment, all of which are based on your character level, as shown in the Training table.
Your training bonus grants you a bonus to attacks, checks, initiative, and saves, as associated with the type of training you have with that roll.
There are five types of training bonuses, each being an increment of the previous one, in the following order:
Untrained. If you lack any training, you are untrained and apply no bonuses (or +0).
Aptitude Bonus (Apt). The aptitude bonus grants a +1 bonus at early levels and a +3 bonus at the later levels.
Proficiency Bonus (Proficient). The proficiency bonus is the most common type of training, starting at a +2 bonus and ending at +6.
Expertise Bonus (Expert). The expertise bonus starts at +3 and ends at +9, being a middle ground between proficiency and mastery.
Mastery Bonus (Master). The mastery bonus represents the ultimate training, starting at a +4 bonus and going all the way to +12.
A training bonus can't be added or subtracted to a roll or feature more than once, and multiple types of training bonuses can't be added.
When a feature grants you a training improvement, your current training bonus progresses to the next order of training, as explained above. For example, if you have proficiency in the Perception skill and a feature grants you a training improvement in that skill, you now have expertise in it.
Some features can grant you multiple uses based on a type of training. These uses are based on the training bonus granted at your level by that type of training. Any expended uses from these features are regained once you finish a 6-hours sleep, unless specified otherwise.
Your training and its associated type with specific equipment grants you unique features while you have them equipped.
Your training with armor grants you damage threshold to bludgeoning, piercing, and slashing damage, while your training with shields grants you damage threshold to cold, fire, and lightning damage. The damage threshold is equal to the training bonus granted by the type of training you have with that armor or shield. You must have the trained armor or shield equipped to gain these features. See more on damage thresholds in the resources section.
If you are untrained and equipped with an armor or a shield, you are hindered, maimed, and you become slowed at the start of your turns.
Training with a focus allows you to use the spells associated with that focus. For example, an arcane focus allows you to use spells from the list of arcane spells. The feature that grants you training with the focus also determines the ability used for the attacks and DC of these spells. See more on spellcasting in the character features section.
If you are untrained and equipped with a focus, you are impaired.
Your training with weapons allows you to add your type of training bonus to attacks you make with that weapon. Training with martial weapons also allows you to use maneuvers and your training bonus with the DC of the maneuvers you use. You must have the trained weapon equipped to gain these features. See more on maneuvers in the character features section.
If you are untrained and equipped with a weapon, you are exposed and staggered.
A training die represents an attempt of overachieving something you have been training for. Your training die is also always based on your character level, not any of your class level. A feature might use your training die in addition to other rolls and bonuses. A training die can't be added to the same roll more than once, but a training die can be added to a roll that already has your training bonus applied to it.