Terminology

You will need a Game Master (GM). A person who abides by the rules and remains entirely neutral in describing and adjudicating the game world. Though they carry great hope for the players at every step, they do nothing to sway fate, and allow the players to live and breathe in the game world as they will.

You will need at least one, and maybe many more Players. They will create characters and send them off to adventure in the game world. Those characters may attempt any action that can be imagined, and the GM will describe the outcome of that attempt. The players act and the GM reacts.

You will need, lastly, some dice, which use the following notation:

d4: a four-sided die
d6: a six-sided die
d8: an eight-sided die
d10: a ten-sided die
d12: a twelve-sided die
d20: a twenty-sided die

There are a few ways that these will be rolled in the game, described as follows:

Skill Check: A roll of 1d6. A value equal to or less than the skill is considered a success.

Untrained Skill Check: If a character has more than 10 in a skill's primary attribute, they may attempt it untrained and succeed on a 1. The results of failure are worse than they would be normally. For example, a trained climber may be unable to proceed, an untrained climber would fall.

Attributes: Some of the innate qualities of a character as a result of the life they lived before adventuring. How Accurate, Cunning, Discrete, Persuasive, Quick, Resolute, Strong, and Vigilant they are. Expressed as a range from 3 to 18.

Attribute Modifier: How far an attribute is above or below 10. For example, a Character with a Strong value of 15 would have a Strength Modifier of 5. Alternatively, with a value of 7 they would have a modifier of -3.

Attribute Check: In situations where characters directly oppose other characters, an attribute check may be used to settle disputes by rolling equal to or under the attribute minus the opposed modifier. For example, a very friendly and good natured character may attempt to convince a frightened person on the other side of a door to let them in a room. The character's Persuasive score of 15 minus the fairly stubborn person's Resolute modifier of 3 means that if the character rolls a 12 or less, they succeed and the frightened person unbars the door.

Success by X: How far the result of a roll is below a target number. For example, if a skill is level 4, rolling a 1 would be success by 3.

Critical Success/Failure: If a result is 10 or more beyond the target number.

Most actions while Exploring take place over a number of Turns, roughly 10 minutes each.

In moments of high intensity where more granularity is needed, the GM may stop the clock and instead move to Segmented play.
Each character present acts in order, with each action taking a Segment, usually a few seconds.
The time it takes all characters in a situation to act out each of their segments is one Round, usually one minute.

There can be any number of segments in a round, 10 rounds in a turn, 6 turns in an hour, and 24 hours in a day.
Do not worry if these numbers are not exactly correct in the moment.
It probably takes more than 10 minutes to disarm a complex mechanical trap through the narrow seam in a chest lid.
It probably takes less than 10 minutes to get a torch out of a backpack and light it.
Some acts will be obviously longer and some obviously shorter, but it will all balance in the end.

X' is used to denote a distance of roughly one square on a map. If you are using the imperial system, this is 10 feet. If you are using metric, this is 3 meters.
5' = 50 feet, 15 meters, 5 squares

No exceptions are intended to be made for diagonals. One square over followed by one square up or down is two squares, 20 feet.
You may, of course, resolve diagonals however you wish. There are many theories and much more complex systems for doing so.
Alternatively, you may use a hex grid.
These options will not significantly change your experience, so use whatever feels best.

1/1' is read as "1 per 1 square" and will usually be encountered as an ability cost, where it means, for example, 1 Corruption for every 1 square of distance.

All basic actions and effects that are the result of normal events are referred to as Mundane.
All fantastic, mystical, or otherworldly effects are referred to as Distortion.
When distortion damages organic things (characters, creatures, and nature), harming them in ways they have trouble healing, it is referred to as Corruption.
Someone who practices sorcery may sense Distortion reverberating through a wall as they witness strange effects in an underground room.
They may then experience Corruption as their body burns and warps while they attempt to channel and control it.

Throughout your adventure, you will lose HP and gain temporary Corruption. Both recover at the rate of 1 point per hour (every 6 turns).
Many other things may cause damage directly to your Attributes. These heal at 1 point per day.
Any points of Corruption beyond your character's Corruption Threshold instantly become permanent. These points are never reduced unless by exceptional means.
Whenever a character gains permanent Corruption, they must pass a Resolute check or take that much damage. If this reduces their HP to 0 or less, they are consumed.

Some abilities and effects have an Ongoing Cost in order to keep them active beyond a single turn.
If it is HP, then the character's maximum HP is reduced by that amount.
If it is an Attribute, then that attribute is reduced by that amount.
If it is Corruption, then the character's Temporary Corruption cannot be reduced below that amount.
This continues as long as the effect is active.
Once the ability is stopped by the character or otherwise ends, anything missing recovers at the normal rate.