sicilian knight takes immediatly

This might seem quite basic, and maybe im just thinking too much but when i look at tutorials on youtube(which is sadly my only source of information)  they never cover this.  in sicilian the mainline i believe follows the order 1.e4 c5 2.Nf3 Nc6 3. d4 cxd4. 4.Nxd4 NxNd4?

Sorry first time typing it out in real chess format lol, but what are proper moves after that? sorry i know this is beginner question but this is the type of stuff that trumps me, when people dont follow mainline lol.  Any feedback is appreciated, thanks

Look at that beautifully centralised queen. White is ready to take a firm grip on the center. Just develop normally, castle and go from there. It's a game of chess

i guess thats my misunderstanding. is it the goal to centralize the queen? thanks for the input i feel i have a tendacy to overreact when my queen is in the center for feelings of being trapped.  It took my VERY long to realize that a queen for rook and minor piece is very fair trade off

 One of the goals of the opening stage is to control the center. Pieces have more scope (attack more squares) when stationed in the center (compare a knight in the center with one on the edge). A centralized queen can be very powerful (but as you said it can sometimes become exposed so you have to guard against this)

Compare the position above with the following from the Scandinavian Defense. Black's queen is centralized but White has the tempo gaining move Nc3 available. Thus, by chasing the queen around, White can gain time to develop his own pieces and leave Black lagging behind in that department.

A queen for a rook and minor piece is often not a fair trade. Queen for rook and two pieces or queen for two rooks is better...but you always have to be wary in these cases because it's easier to play with a queen, two rooks especially can be difficult to co-ordinate properly.

thanks arctor, much appreciated and this is actually the exact move opening i had in my with regards to not allowing my queen in the center. Obviously it is different because white has tempo perahps i simply need to relax when i have tempo? lol I started playing chess in results to brain trauma and having the doctors say that games such as chess along with random activites such as shooting free throws, walking etc were good for ne neuronal growth so i have a tendacy to not see things clearly, so queen in center can be abig problem for me.  Thanks for the input much appreciate

Honestly, most players with black would not take on d4. This is true for the Sicilian and also for the Scottish game, which is the same idea except black played e5 and not c5. Yes, a central queen is vulnerable, so being active too early can result in attacks. At most that will cost you 1 or 2 tempo/tempi, so for most players the difference is very subtle.

Now, if black takes with the knight, one attacker is already gone, so the queen isn't that vulnerable. Besides white must recapture somehow. In this case you recapture with development or with tempo. Black's capture developed nothing. These are all good reasons why the queen is well placed.

When I was learning to play chess, the old men at the club taught me a valuable technique for deciding whether or not opening exchanges were to my benefit.

It's called "counting tempos" and works like this:

Counting White:

I count one for the pawn on e4.

I count one for the Queen on d4.

Total is two.

Counting Black:

I count zero for developed chessmen.

I count one because it is Black to move.

Total is one.

Conclusion:

The exchanges in the centre favoured White because he gained one tempo (2-1=1).

(To say nothing of the beautifully centralized White Queen, that others have pointed out) 

Time is very important in chess and shouldn't be frittered away carelessly.

Taking things a little further:

The position is particularly strong for White because he can play for the Maroczy Bind formation with Black's "useful" knight missing.

Take a look at this:

That's my take on the position, anyway.

Basically not a great idea to use the queen early in the game, just a tip

Read the thread before posting.

Just a tip.

windows, that was my understanding but obviously in this position with the knight taking you must take or be down a minor piece.  Essentially i was looking for WHY at higher level you dont see this play and i think the posters have done a solid job of pointing out the strengths associated with it.  Thanks guys small question i know but helps alot