or
A WORLD OF SPIT!
The overall system can be captured by the acronym SPIT: Surprise, Positions, Initiative, Turns
Immediately after entering combat, a few things need to be established explicitly – these are the Surprise, Positions, and Inspiration.
The Turn step is repeated until the encounter is over.
S – Surprise
Basically, does anyone have the jump on anyone else.
This is done via Stealth vs. Perception check and is only relevant if the situation makes sense. Perhaps you are behind a tree attempting an ambush (You would get the Stealth roll); perhaps you were unknowingly being followed by a band of disgruntled postal workers (the postal workers get the Stealth roll).
If Surprised, a character loses their turn for the first Round of combat. This includes losing the ability to have Reactions for the entire Round until their first Turn on the next Round.
P – Positions
Typically the DM would decide where everyone is located, but will most likely be based on the marching order (the positions you guys formed while walking/before entering combat). When necessary, the Players will be able to fine tune their position, based on terrain, etc. This is on a case by case basis.
I – Initiative
This tells us the order in which people are able to react to the situation.
Simply roll 1d20 and add your Inititative modifier.
The next step (Turns), will be take in the order of highest to lowest Intitiative (after applying mods).
T – Turns
This step is repeated until the Encounter is over as a series of Rounds.
A Round is a single cycle of ALL the participants (including NPCs) taking their Turn.
A single Round can be thought of as a 6-second span of time.
All of the actions across an entire Round are considered to be happening almost simultaneously. Anything that could reasonably be done in a 6-second window, can be done in a single Round.