The best way to understand how bands make reggae tracks is to listen to lots of reggae, paying attention to what each instrument is doing.
The most basic analysis of reggae is this:
- the bassline is prominent, slightly weighted towards the third beat of each bar.
- some other mid-to-high range instrument plays staccato chords on the second and fourth beat of each bar. Sometimes it's guitar, sometimes organ, sometimes piano, sometimes something else. This is sometimes called the "skank", because it sounds like that.
If you play a song like "Twist and Shout" emphasising the first and third beats, it will sound like rock. Emphasise the second and fourth, with a skank as above, and it will sound like reggae. There are lots of reggae versions of "Twist and Shout" you could check out to demonstrate this.
Follow this format exactly and you'll end up with a disappointing, lumpen version of reggae. Listen to good reggae and you'll notice how other touches, and simply the swing of it, lift it and improve it.
I suspect when your friends say "reggae chords" they are referring to the skank. Since you mention DJing, I wonder whether you are trying to make reggae by putting skank from one record on the singing from another. This can only work if the two songs have the same chord progression. It's no use having a bass playing E, a piano playing an F chord and a singer singing F sharp; pitches need to sound nice together.