- Yes, we need ready action, together with proper reactions.
- No, ready action is not the same as delay turn.
Ready means you use your action and say: "When this happens I will do that action as reaction." Usually you select "When an enemy moves to a position I can target then I attack it with my equipped weapon or a spell I have selected." So you act first when the conditions are met and maybe you can kill an enemy once he enters the room before he can do anything.
Imagine an enemy mage is in the next room (low HP and AC, powerful spells). You can:
- Walk in the next room and end your turn because he is too far away. He will kill or CC you on his next turn.
- Delay your turn. The enemy will enter the room and kill or CC you on his next turn.
- Move to the door so you can only be seen from within the room and ready your attack. When the enemy enters the room you attack him before he can act.

Prof. Dr. Dr. Mad S. Tist

World leading expert of artificial stupidity.
Because there are too many people who work on artificial intelligence already