Slash chords have two symbols. There's one on the top, and one on the bottom, usually with a slash separating the two. Sometimes you can have a forward slash, almost like a fraction, or you can have a horizontal slash with a chord symbol on top and another chord symbol on the bottom.
The top one, to keep in mind, is the actual chord. So if you have a C on top and an E on the bottom, what it's telling you is to play a C chord, but with an E bass note. So therefore, it won't sound like this [playing chord], it will sound like this [playing chord]. So, I'm playing my low E on the bottom.
That just happens to be the example that I gave you, just happens to be an inversion of the C chord. We have one of the chord tones on the bottom. It's not always one of the chord tones on the bottom, it can be a non-chord tone on the bottom.
So, let's say we have C over F [playing chord]. This would be a great way to play the C major chord, but have the F as the bass note.
One really good way to explore slash chords, is to try picking a scale and using the scale tones on the bottom as your bass notes.
So, let's try this. Let's go C [plays note], C over C you could say, even though that would be an incorrect way to write it out, but let's just call it C over C for now. C over D [plays chord], a very different sound. C over E [plays chord], C over F [plays chord], you can also play C over F like that [plays chord], C over G [plays chord], C over A [plays chord] which is really just A minor 7, but for all intents and purposes of this lesson we'll just call it C over A, C over B [plays chord], back to our C major chord [plays chord].
Now to get some more creative sounds out of it, let's explore some chromatic notes. Some of these might not sound so pretty, but let's explore them anyway. So, we'll go C over C [plays chord], C over D flat [plays chord], back to our C over D like we did before [plays chord], C over E flat [plays chord], C over E [plays chord], C over F [plays chord], C over F sharp [plays chord], C over G [plays chord], C over G sharp, or A flat if you prefer [plays chord], C over A [plays chord], C over B flat [plays chord], C over B [plays chord] and C [plays chord].
So the main thing is, when you see a slash chord is play that chord on top, and find the bass note on the bottom, and there's your slash chords.