As a result especially of a failed action roll or a partial success, consequences may befall the character. Consequences also follow an NPC action that you choose to not resist.
The failure results in the loss of an opportunity so that the situation in the fiction changes for you or the entire party.
This could be that while sneaking around you are spotted. Your opportunity to do something unseen is now lost. An alarm will be raised and you have to face whatever happens as a result.
You have lost or given up your position and if the encounter continues your next action rolls will be done with a worse position.
You suffer actual physical harm. This is a common consequence in combat, but can also happen in other actions such as failing a jump and falling, etc.
When suffering harm, you take one box of either lesser, moderate or severe damage. Which damage you take depends on the circumstances.
Here are some guidelines:
Something else happens in the fiction that goes against you, depending on the situation.
This could be some of the enemies escaping, or a hostage getting hurt, equipment lost or damaged or similar things. It can also be that some progress bar running against you gets a box marked.