Dsk,
Flaperons are basically a mix of flaps and ailerons. On a full scale plane it will have both flaps and ailerons, but since most of our planes aren't built with both you can get the same effects by using a computer radio to mix together the two functions onto one control surface, thus you have flaperons.

You already know that the ailerons cause the plane to roll, but he effects of flaps can be confusing to newer pilots. Flaps are a control surface that extend down from the trailing edge of the wing. What this does is basically increase the surface of the wing, which will produce more lift from the wing. Full scale planes use them to take off and land. Extending the flaps let's the wing produce more lift for takeoff, and will let the plane fly slower to land.

When you mix them into our planes the ailerons will extend down into a flap position, but will still let you move them with the aileron controls to correct directions changes. When you extend the flaps down the extra drag causes the plane to slow down and thus dive, which you have already noticed. You can correct that with elevator, or by giving the plane a bit more power. How much you use when taking off and landing depends on the plane. With a SSE they really aren't needed. But if you want to play around with them I would recommend that you make approaches at a mistake or two high, and start applying the flaperons. Try just a little bit at first until you become more comfortable with the way the plane handles with them.

Hope this helps

Ken