Nothing to so with Guns n Roses, and you don't play two chords at once either!
Slash chords are really simple. You will often see chords like D/F# or Am/G. Don't be afraid :)
All is means is CHORD / BASS NOTE!
It's that easy - the first letter is the chord and the second is the bass note. Often you don't have to worry about playing the bass note - let the bass player do it - but if you are playing by yourself then it is often sounds better to put in the suggested bass note. You can assume it will make it sound better or more like the original tune.
Some of the most common are shown in the video - I will get some chord boxes up here soon but for now you will have to rely on my mini tab below... the chord boxes take ages to make and it's getting late and I have not had my dinner yet ;)
D/F# = TAB: 2 x 0 2 3 x
G/B = TAB: x 2 0 0 3 x
Am/G = TAB: 3 x 2 2 1 0
A/C# = TAB: x 4 2 2 2 x
A/G = TAB: 3 x 2 2 2 x
A/F# = TAB: 2 x 2 2 2 x (also known as F#min7)
Don't forget to experiment yourself too - it is easy and quite fun to try and find your own cool slash chords.
Also work on the sequences below, because they are really common, and you will probably use them a lot:
1. G - D/F# - Em and back again... like Em - D/F# - G
2. C - G/B - Am and back again... Am - G/B - C
Have fun dudes and dudettes, J