Theory:

     The second way of putting out a fire is to prevent oxygen from reaching it. No supply of oxygen means no fire. Small fires can be put out or ‘smothered’ with a damp blanket or a sack. This stops oxygen reaching the burning material. Sometimes, carbon dioxide is used to extinguish fire. It does not allow oxygen to reach the burning material.
Explanation:
  
The second method of putting out a fire is by preventing oxygen from reaching it. Oxygen is vital in sustaining a fire. If you take the oxygen away, you end up putting out the fire.

Have you come across the candlelight experiment? It is about how you can put out a candlelight flame after covering it with a tumbler.
fire useful collage (2).jpg
 
When you cover the candle with a tumbler, you end up depriving the candle the oxygen it needs. When there is no oxygen, there would be no fire.

That is also the reason why carbon dioxide is used as a fire extinguisher. Carbon dioxide will not allow oxygen to reach the burning material, and hence, the fire will stop blazing.

andrei-slobtsov-7RfP8lLkHwI-unsplash.jpg
Fire extinguisher

You can also put out a fire by throwing a wet sack or blanket (thick cloth) on the burning material. This will prevent oxygen from entering the material.
 
kalei-peek-goRfueKTDA4-unsplash.jpg
Sack
 
Meanings of difficult words:
 
No.
Words
Meanings
1
SmotheredExtinguish a fire by covering it
2
DampSomething which is wet
3
ExtinguishCause a fire or light to stop to burn or shine
Reference:
National Council of Educational Research and Training (2007). Honeycomb. Fire: Friend and Foe (pp. 114-118). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.
 
Video courtesy: https://www.youtube.com/watch?v=68O2Ea-hUsE