These are the basics.

Ability Scores

You begin the game with six values (3, 2, 1, 0, 0, 0) to be assigned to the six ability scores however you desire.

Optionally, you can apply -1 to a score to gain +1 to another score (though you cannot increase the 3 to a 4). You may do this twice if you prefer, applying the -1 to a different stat each time.

Every level, you gain two +1 proficiency bonuses to two different ability scores of your choice.

Foundation

You begin the game with three Foundation levels which grant three Feats from the Ancestry or Background types.

Class and Level

When you gain a level (including 1st), you increase your chosen class by one level.

Yes, multiclassing exists.

Pretend I explained it all here.

Rank

Depending on your current level, you also have a "rank":

Some abilities hae a required rank to use and/or acquire.

Damage

Any time you encounter the words "light", "medium", or "heavy" in concert with "damage" (e.g. medium fire damage, light slashing damage), it refers to a standard amount of damage based on your rank, proficiency, and ability scores:

The value "x" refers to a modifier containing:

• the ability score used to inflict the damage
• your proficiency bonus, if proficient in the attack