The game organizes the chaos of combat into a cycle of rounds and turns. A round represents about 6 seconds in the game world. During a round, each participant in a battle takes a turn. (90)
Combat Step by Step
1. Determine surprise. The GM determines whether anyone involved in the combat encounter is surprised.
2. Establish positions. The GM decides where all the characters and monsters are located. Given the adventurersʼ marching order or their stated positions in the room or other location, the GM figures out where the adversaries are - how far away and in what direction.
3. Roll initiative. Everyone involved in the combat encounter rolls initiative, determining the order of combatantsʼ turns.
4. Take turns. Each participant in the battle takes a turn in initiative order.
5. Begin the next round. When everyone involved in the combat has had a turn, the round ends. Repeat step 4 until the fighting stops. (90)
Move & Action. On your turn, you can move a distance up to your speed and take one action. You decide whether to move first or take your action first. Your speed - sometimes called your walking speed - is noted on your character sheet. You can forgo moving, taking an action, or doing anything at all on your turn. If you can’t decide what to do on your turn, consider taking the Dodge or Ready action. (90)
Bonus Actions. Various class features, spells, and other abilities let you take an additional action on your turn called a bonus action. (90)
Other Activity on Your Turn. Your turn can include a variety of flourishes that require neither your action nor your move. You can communicate however you are able, through brief utterances and gestures, as you take your turn. You can also interact with one object or feature of the environment for free, during either your move or your action. (91)
Reactions. Certain special abilities, spells, and situations allow you to take a special action called a reaction. A reaction is an instant response to a trigger of some kind, which can occur on your turn or on someone else’s. (91)