What makes c4 and c5 good??

Obviously e4/5 and d4/5 allows scope for you bishop, and room for you queen to breath as well as control of two central squares. The c file openings only get 1 central square, and do not create scope. Why do we still continue to play it though??

I don't :)

haha, I have played it once or twice.

Well, for white, it is named the English opening, which allows you to later push d4 and e4, creating a huge center. For black, it is named the sicilian, which is one of the best moves for black, almost equalizing the position.

how does it equalize the position???

It's a really good question, and the answer lies in the history of chess openings.

For a long long time people played e4 to get the fastest mating net possible(Bc4, Nf3-e5, Qf5 or Qh5). And black played symmetrically...

Then, white players found out that moving d4 prevents black's e5, possibly getting central control and more probably forcing black to play e6, creating development problems for at least one bishop for black player.

Then, white understood that d4 can be met by either d5 or Nf6, restricting their own e pawn as well! Furthermore, if white plays Nc3 to strengthen this square, then the c pawn is blocked. Further further more, the blocked c pawn also blocks queen's access to d1-a4 diagonal. People understood that using this diagonal, there are tactical and strategical options. To benefit from the positional gain, people also discovered 1.Nf3 d5 2. c4 or directly 1.c4. This move gives queen d1-a4 diagonal, and also when Nc3 is played, c pawn won't be blocked.

Further further further more, these cheesy tactics starting with c4 mostly converge on c6 square in the enemy territory, forcing enemy to put a pawn rather than a knight at this square, for example:

I think that's why c4, and also Nf3 are good alternatives to play. This chess opening history thing goes until white plays 1.a3 and 1.h3, and even justifies those moves as well. So today, it's fine whatever you move in the first move, so long as you have a plan.

ok, thank you very much, that was interesting and helpful

people play 1.c4 or 1.Nf3 generally to avoid some of black responses.

catch is  , with 1.c4 white can avoid the popular Nimzo-Indian but now he must know how to reply to 1.c4 e5 and to some other options black now have . there's no such thing as an ultimate opening . each opening has it's own strengths and weakness ...

1.c4 controls square d5 and prevents 1...d5. Opening space for piece development is not an issue, as the light-squared bishop is usually fianchettoed, in order to exert control over square - surprise! - d5. Furthermore by keeping both central pawns behind, white can later make many different strategical choices about the ensuing pawn structure.

1...e5 certainly is the critical response, but practice shows that in the reversed Sicilians white has chances to play for an opening advantage as in any other good opening.

And no, moves like 1.a3 or 1.h3? will never have relevance to opening theory. The best moves are 1.c4, 1.d4, 1.e4 and 1.Nf3. Also not bad is 1.g3, because black can hardly avoid transposition into an Englisch, Catalan, Tarrasch, or another respectable opening. The rest is substandard and cannot be used on a regular basis on master level and above.

Thanks

I've only now been looking at that opening fragment here. So black made a mistake on move 5 (?), which was exploited by a strong white move 6 (!), and yet "the position is about equal"? How would that be possible? If the position is equal, then either black's play was good, or white's play was as bad and deserves a question mark, too.

Of course the moves and the assessments have several flaws. First of all, on move 4 and 5 white should have taken on d5. Instead he hands the centre to black, who can make use of this in several different ways.  5...dxc4 is not at all a mistake. White has to make some queen moves to win back the pawn. That said, 5...e4 might be stronger. Also the reversed Benoni after 5...d4 offers black a pleasant position.

And why did black play 6.Bd7 and not Bd6? He simply squandered a full tempo here. 

It is a good question, but I don't think anyone has answered it well yet.

Let's compare 1.d4 d5 to 1.e4 e5.  After the latter, White commonly plays 2.Nf3, which is a threat to capture the black e-pawn, and to which Black has to respond.  After 1.d4 d5, however, 2.Nc3 is not effective in the same way, because the queen defends the pawn.  Since straightforward piece play is ineffective at creating threats in the center, White must hit at d5 with a pawn first -- hence, c4.

The same principle applies to the assorted move orders of the flank openings.  1.c4 is contesting control of d5, without committing to where White will put his d-pawn.  Converse examples from the black side (e.g., Benoni 1.d4 Nf6 2.c4 c5) have a similar rationale as well.

here is typical low level c4 game 10 0 

had black not 10... Na5 I would have tried to develop my dark bishop and rook on a1 to c1 ??

I like c4 for its solid pressure on the center and flexablity.  Unlike coming with d4 straight away I find many more mid game goals are available. 

ok, thanks to all who have answered