What are the principles for time delay relays ?

I read an electronic magazine in which there is a report on what are the principles for time delay relays. After reading, I became interested in the principles for time delay relays. So I searched some related materials and information about this topic from google. Today I come to this forum to turn to you to discuss my understandings are appropriate.

Here are my personal understandings:

Power delay time The relay has a delay normally open contact, delay normally closed contact, instantaneous normally open contacts and instantaneous normally closed contacts. The principle is as follows: When the power-off delay time relay "coil" power off: delay normally open contact - after the set time after the opening delay normally closed contact - after the set time after the turn on.
Delayed relays are mainly used for DC or AC operation in a variety of protection and automatic control lines as auxiliary relays to increase the number of contacts and contact capacity. You can adjust the delay time as needed.

Delayed relays are an alternative to conventional industrial relays by reducing the energy consumption of the automatic delay load, reducing user comfort (eg, ON-OFF switches while controlling lighting and ventilation). Modular structures can provide more benefits.

Ps: Excuse me if I was wrong in words or expressions as I am a green hand in the field of time delay relays. I need continual learnings.

What is your idea ? Do you agree with my ideas ? Any of your ideas would be highly appreciated.

May someone would like to help ?

thanks in advance