Combat is in rounds and turns. Round is time what takes all participants to make their actions, turn is one individual's action. Time of one turn or round can vary greatly. In fast phased gunshooting one turn can take few seconds to fire a gun, but in space combat one turn can take several minutes to manouver the spacecraft.
Initiative determines the order in which participants act. Usually player characters roll individual initiative, but gamemaster can roll single initiative roll for every NPC/monster with same basic initiative value.
Initiative can be re-rolled after every round, or first initiative can be used through whole combat. Highest initiative score gets to act first, second highest gets to act second and lowest gets to act last.
Character can also delay his action from his turn and act in any initiative turn he wants.
Basic initiative is character's Dexterity + Perception.
Add result of D6 to basic initiative to determine each combatants phase to act in combat round. If you score result 6 with D6, roll again. Second roll is another action's turn in one combat round.
Character's Dexterity is 3 and Perception 4, so basic initiative is 7. Result of D6 roll is 3, so character's turn in combat round is 7.
Character's Dexterity is 3 and Perception 4, so basic initiative is 7. Result of D6 roll is 6, so player gets to roll D6 again to score 3. Character gets to act in turns 13 and 3. With exploding die he gets to act two times in combat round.
These extra actions don't suffer negative modifiers.
More Than One Action In Turn
Character can take more than one action in a single turn. Every additional action adds one negative modifier to every roll. Three actions is maximum to perform.
Two actions in one turns is 2 negative modifier for both acts.
Three actions in one turn is 3 negative modifier for each acts.
In each extra action from exploding initiative die you can perform more than one action, but each extra turn is dealed individually.
Character takes three actions in his combat turn. He rolls his every act with three negative modifiers.