This is called the 1-3 rhythm because - well because you play on the 1st and 3rd beat of the bar.
This is the "stop rhythm" and it's more often used to add some variation within a piece than as a steady rhythm figure throughout the tune.
Damping
There are two ways to play the 1-3 rhythm. We can do it as above, or we can dampen the strings on the seacond and fourth beat:
Remember to keep your right hand going in a steady time. On the first beat you stroke the strings, on the second you hit them softly with your hand to stop the sound and so on.
Backbeat
Remember Chuck Berry's hit "Rock'n roll music?" One line of the lyrics is "It's got a backbeat you can't loose it."The backbeat (or 2-4 rhythm) is useful for much more than rock though. In irsh music we usally play it when we have some other instrument taking care of the first and third beat, but it can be effective on its own as well.
If you have the 1-3 rhtyhm with dampings down, the backbeat is easy. You just turn it around the other way:
