Theory:

Conjunctions are words that link other words, phrases, or clauses together.
Example:
1. Radha likes cooking and eating, but she doesn’t like washing dishes afterwards.
2. Sita is clearly exhausted, yet she insists on singing till evening.
Conjunctions allow you to form complex sentences.
There are three types of conjunctions:
I. Coordinating conjunctions allow you to join words, phrases, and clauses of equal grammatical rank in a sentence. The most common coordinating conjunctions are for, and, nor, but, or, yet, and so; you can remember them by using the mnemonic device FANBOYS.
Example:
1. I’d like idly or dosa for dinner.
2. We needed a place to study, so we took our things and went to the library.
3. Jessica didn’t have much money, but she went ahead.
Important!
Notice the use of the comma when a coordinating conjunction is joining two independent clauses.
II. Correlative conjunctions are pairs of conjunctions that work together. Some examples are either/or, neither/nor, and not only/but also.
Example:
1. Not only am I finished studying for Biology, but also finished writing my English essay.
2. Sheela can have either tea or coffee.
III. Subordinating conjunctions join independent and dependent clauses of unequal importance. A subordinating conjunction can tell a cause-and-effect relationship, a contrast, between the clauses. Common subordinating  conjunctions are because, since, as, although, though, while, and whereas. Sometimes an adverb, such as until, after, or before can function as a conjunction.
Example:
1. Rima can stay out until the clock strikes eight.
Here, the adverb until functions as a coordinating conjunction to connect two ideas: Rima can stay out (the independent clause), and the clock strikes eight (the dependent clause). The independent clause could stand alone as a sentence; the dependent clause depends on the independent clause to make sense.
 
2. Before he leaves, make sure his room is clean.
If the dependent clause comes first, use a comma before the independent clause.
Subordinating conjunctions may be sub-divided into four types:
  1. Conjunctions of time: Example: While, before.
  2. Conjunctions of place: Example: Where, wherever.
  3. Conjunctions of concession: Example: Though, although.
  4. Conjunctions of comparison: Example: As, than.
List of conjunctions:
1. Some Coordinating Conjunctions are:
for, and, nor, but, or, yet, so, as well as, else, otherwise, still, while, however, consequently, etc.
 
2. Some Correlative Conjunctions are:
both/and, either/or, neither/nor, not only/but, whether/or, rather than, whether or etc.
 
3. Some Subordinating Conjunctions are:
after, although, as, as if, as long as, as much as, as soon as, as though, because, before, by the time, even if, even though, if, in order that, in case, in the event that, lest, now that, once, only, only if, provided that, since, so, supposing, that, than, though, till, unless, until, when, whenever, where, whereas, wherever, whether or not, while etc.
Conjunctions used in the lesson "Sir Isaac NewtonAn Ingenious Scientist":
  1. Little did his mother think, when she beheld her new-born babe, that he was destined to explain many matters which had been a mystery ever since the creation of the world.
  2. Mrs. Newton was married again to a clergyman and went to reside at North Witham.
  3. No fear but what Isaac will do well in the world.
  4. There was some ground for supposing that Isaac would devote himself to the manufacture of clocks; since he had already made one.
  5. It was set going, not by wheels and weights, like other clocks, but by the dropping of water.
  6. While the mill was at rest, he pried into its internal machinery.
  7. After gaining a thorough knowledge of its construction, he was observed to be unusually busy with his tools.
  8. Though not so large, I suppose as one of the box-traps which boys set to catch squirrels, yet every part of the mill and its machinery was complete.
  9. But his mind was so bent on becoming a scholar, that his mother sent him back to school, and afterwards to the University of Cambridge.
  10. The story of an apple falling on his head which lead him to discover the force of gravitation and which keeps the heavenly bodies in their courses.
  11. He never permitted his mind to rest until he had searched out all the laws.
  12. While researching, he was accustomed to spend night after night in a lofty tower.