chord combinations

I am a beginner. Is there some site I can find out about chord combinations like D/C, D/Bb, etc. I don't quite understand this concept.

Those are called 'slash chords', and they're pretty simple. All they mean is that you would play the chord as usual but add the note after the slash as the lowest note. For example, you mentioned a D/C. Just play a D chord as normal, and also play the third fret of the fifth string (a C).

The note that comes before the "/" is the chord, in this case D, the note that comes after is the bass note, so the lowest note. D/C would look something like this:-

EADGBe
x3x232

Make sense?...Hope so...Good luck, feel free to ask if there's anything not clear!

you can also use the name polychord for this kind of chords, because most of them are 2 triads of 2 different chords put on top of each other... My contribution is totally useless, and you won't play better by knowing the word but hey, you might impress a girl with it!

not exactly true, sometimes a slash chord is an inversion ex; C/G
also, when dealing with triads I don't know if I would want to think of these as poly chords; D/C Dmaj & Fmaj?

I would reserve my polychordal thinking for 9th 11th & 13th chords...ex; C9, cmaj & Bdim.

I said my contribution was useless, but actually, those chords are named polychords by several players (Franck GAMBALE's one of them)... I also think that you can name them inversions, different root chords, or nifty little dang stuff that sound awesome, it's totally useless to know the name, as long as you can play them and enjoy it...