you got to understand what scales are. i dunno how to explain a scale.... well let me try... you know DO RE MI? THATS a scale. a major scale for example has 7 distinct notes, that can be expressed as "do, re, mi, fa, sol, la, ti"
when 3 notes or more from a scale is played in a beat, it is called a chord.
i wont go into detail about chord construction, my theory sucks and if you really want to learn you can read it up
i think your confusion stems from the fact that a "C chord" is implied to be a C major chord, while a C note is just a note. why it is like this, i really don't know, you got to ask those lazy guitar mofos
in the C major scale, there are (or rather, happens to be) no flats or sharps. so a C major scale would consist of the notes C, D, E, F, G, A and B. in a minor scale, lets say C minor, the notes are C, D, Eb, F, G, Ab and Bb.
why it is like that, is up to you to find out
in both the C major and C minor scales, C is the root note. for simplicity's sake let's just call it the 'first' note. all the notes that come after it depend on which scale it is.
there are tons of scales, major, natural/harmonic/melodic minor, pentatonic major/minor, blues, bebop etc.