Twins are two endgame studies that look very much like each other but only differ in one tiny detail.
Since you've got only one study there, there is probably something missing. Were there two diagrams, or instructions not exactly "White to move and draw" ?
Another example is http://ruszchessstudies.blogspot.com/2008/02/study-29.html
There the instructions are "Win; Twin B: Qe4->f3"
Which means
1) In this version (twin A): White to move and win
2) To get to twin B, place the black queen from e4 to f3. Then, white to move and win.
And that tiny detail turns out to have a very different solution.
In a twin study There is an extra stipulation, it is Written Something like this: Kf7-e7 (which would mean you now have a different problem, with the Black King on e7) or Bwa1 (which would mean you have a different problem with a white Bishop added at a1)
Do you see something that resembles this in your Diagram?
From the February 2009 Chess Life...
"Twins are rare in artistic endgames. The main reason is that the composer must discover and combine ideas with only one change in the original starting position. This task has become easier due to computers.
Acceptable changes include moving a piece from one square to another, removing it, or replacing it entirely with another piece. Most gratifying is when a small change yields a big effect. It is both surprising and amusing when distinct ideas are hiding in two practically identical positions. This month we will briefly review some technical aspects of the twin."
Here is an old example:
1. Rh3 d2 2. Rc3+ Kb2 3. Rb3+ Ka2 4. Kc3, Draw.
Could someone please explain the two paragraphs as they make no since to me whatsoever. I'm no titled player but I thought I knew the game fairly well and have never heard of this twin thing. This seems like a simple drawing exercise to me.