Theory:

A preposition is a linking word, that is placed before a noun (or a pronoun) and establishes the positional relationship with other words in the sentence.
In simpler words, a preposition is a connecting word, that links the noun/pronoun with the verb/adjective in the sentence.
Example:
She is sitting on a chair.
 
She - pronoun
Sitting - verb
On - preposition
Chair - noun
 
The preposition (on) connects the pronoun, verb and the noun.
Important!
Prepositions, as the name suggests, usually denote the position of the subject in the sentence.
Take a look at the following:
 
1. It usually rains in September.
2. I usually sleep early at night.
3. Since 2015, I have stopped eating sugar.
4. Before 2004, there were many problems in our society.
5. I'm on leave till 24th of this month.
 
The emphasized words establishes a connection between the noun and the other words in the sentence.
  
Prepositions are of different types. Let us look into each type in detail:
 
prepositions type3.JPG
 
Here is a list of commonly used simple prepositions:
 
atinby
underoveron
besidetofor
overthroughacross
withsince
off
abovenear
from
  
Some of the compound prepositions are
  
aboutabovebelow
alongacrossamidst
aroundbeforebehind
besidebetweenbeneath
 
Here is a list of some participle prepositions:
  
barringconcerningconsidering
duringnotwithstandingpending
regardingrespectingprovided
 
Here is a list of common phrasal prepositions:
  
according toin place ofwith reference to
by means ofin spite ofin front of
for the sake ofwith a view toowing to
in lieu of with regard toinstead of
  
Prepositions can be classified on the basis of its functionality. The prepositions used are the same in both types of classifications.
  
prepositions type2.jpg
 
Some of the examples from the lesson Fire: Friend and Foe:
  1. Long before he began to use fire himself.
  2. The oxygen in the air combines with fuel.
  3. When you blow on smouldering paper, it often bursts into flame.
  4. Every fuel has a particular temperature at which it begins to burn.
  5. We spend millions of rupees each year in fighting fires.
  6. Now there are laws about building construction.
  7. One of the three things needed for burning is taken away.
  8. If the temperature can be brought down below the flash point, the fuel stops burning.
  9. You remove the hot air around the flame.
  10. They can help people suffering from burns.
  11. Fuel and oxygen do not make fire by themselves.
  12. It only means that fire is very useful as long as it is kept under control.