scales

I am trying to gain a thourough understanding of scales and what makes a C maj scale a c major? surely it is not due to the amt of C's in the scale so what does make it a Cmaj or an A maj scale?

im gonna add a question here. so if i know the scale well, and know my chords well. if i play chords that all fall into the scale, will all the chords i get like that work well with eachother? giving them a patern that works well that is. im asking if i give it a good patern will all/most the chords interlock with eachother???

Yes (???)