What is the significance of openings? I am a beginner in chess and don't understand the concept of openings at all. To me they appear to be just moving one of the eight pawns or one of the two knights. But wherever I see there is talk about opening games and they have many names like Sicilian Defence, King's Indian Gambit, etc. What is the need to differentiate them with so many names, for after all as I mentioned earlier, it is going to be one of the eight pawns or one of the two knights?
INTRODUCTION AND RELEVANT INFORMATION:


  I am a beginner in chess and don't understand the concept of openings
  at all. To me they appear to be just moving one of the eight pawns or
  one of the two knights.


This is the root of the problem, and the reason why you have asked the question-it is the consequence of your ignorance.

POINT #1:

You must understand that human being plays the game, and human beings have likes and dislikes. Some of us prefer sharp and fast struggle, and some of us like slow and safe maneuvering, and so on...

POINT #2:

You do not appreciate your turn to move, but in chess, this is very important to master. 
You see, when it is your turn to move, you have a choice, and this is really important.
This is the moment where you have a say, and you can change the course of the game to your like ( see the POINT #1 ).

This is one of many things that differentiates master from novice-master enforces the pace of the game, while beginner complies/plays any move without careful thinking, which results in him/her lamenting later " How did I get into such a horrible position??? How did I blundered a bishop?? " and so on. In chess, this is called tempo.

You must comprehend that you too are the factor in the game, and that this is collision of characters.You must comprehend that not only you play "against pieces" you play against another human being.

Your approach to the game is faulty, because you " dissect " the game, and probably in your opinion there are 3 parts of the game:


Opening
Middlegame
Endgame


This type of division is old and inefficient.

In order to understand my answer, and other answers provided from different members, you must change the approach.

You open the game in order to develop pieces the best way to carry out your middlegame plan, and your middlegame plan is based on the possible events that might take place in the endgame ( chess rules can help you in this, serving as a beacon to follow, but true mastery comes when you learn when to break them-that comes with experience ) .

This is the approach that is the most efficient, in my opinion.

ANSWER:


  What is the significance of openings?


Openings help you to determine what type of opponent is playing against you-does he/she like fast, open battle, or slow and maneuvering one, does he/she aim for endgame or mating attack and so on...

Opening allows you to choose how to tackle those opponents, and enforce them your style of play.

A small example:

Let us say your opponent opened with 1.e4 and you do not want open battle.Let us assume that you like slow maneuvering battle, and feel comfortable playing endgames. In that case you would like to answer with a move that doesn't force early conflict but allows you to choose the moment when the big battle will take place. You could play 1. ...c6 and be confident that the further development of events will be suitable to you.

But what if you want the opposite? What if you want a fast, sharp, open battle?
Then you could reply with 1. ...Nf6 for example. Notice the change of the rhythm:
In the first example White had a choice after Black's 1st move, but now is forced to play with the e-pawn or to defend it.This small example fantastically illustrates POINT#2 from the introduction ( in fact, the whole opening does, and is called Alekhine's defence ).

In open positions, you do not get static solidity and you have to adapt to the changes in the position "on the fly".
In closed ones, your position is solid but you usually need a lot of effort to generate counterplay.

To resume:
Opening helps you to reach the positions that suit your stile ( style being your character/skill level... ) and their knowledge helps you to prepare the position to transpose into middlegame that also corresponds to your style, as well.
Knowing the opening means that you will not be defeated in first 10 to 25 moves, and gives you certainty that you will have an enjoyable game with equal chances to win.


  What is the need to differentiate them with so many names, for after all as I mentioned earlier, it is going to be one of the eight pawns or one of the two knights?


The classification of the openings allows you to find the opening you wish to study, and the openings you wish to prepare against.

These are generally classified as follows:
A ( unsorted ), B ( semi-open games ), C ( open-games ), D ( closed games ), E ( semi-closed games ).

There is an overwhelming amount of moves/move orders and so on, to study and so many openings with the same general idea, but different implementation so you might want to look at them all and choose the one that suits you the best.

Another small example to illustrate this:
Let us say that you are slow, endgame oriented player.
You need an opening that gives you solidity in the beginning, and an advantage in the endgame.
Let us say that you want to prepare against 1.e4.
You could choose 1. ...c6 or 1. ...e6, but although they have the same concept ( repel White's initiative and smash him in the endgame ), there are differences:
The first choice offers harder time to generate counter play, but you have no weak pieces, yet the other one generates counter play easily at the expense of the weak piece ( the light squared bishop ).
Two openings with the same idea, but the implementation of it is drastically different,and only one of them will suit to you.
After you pick one of them, another question arises: Which particular variation in that opening suits your style?
Now comes the strength of POINT #2 into play!
Let us say you have picked 1. ...e6, and let us start "studying" it for a while:
1. e4 e6
2. d4 d5 
3. Nc3 

A "sharp, fast paced, open battle" player would choose 3. ...Bb4 here forcing the matters, while the slow, solid one could try with 3. ...dxe4, for example, simplifying and slowing things down a bit.

Let us assume that you decided that the second option suits your style and you wish to study that.

But how will you find material for this opening?

Well, first you search the name of the opening-it is French defense.
Then you search its general code-it is C.
Then you search the variation you are interested in-it is 10.
So the opening code is C10.
And now you can find online materials/books on the opening you want to play.

Sorry for the lengthy post, hopefully it will help you.
If you have further questions ask, and I shall answer them as soon as I can.
Best regards.