What does this do?

[Halflap]

My flashgun has a diffuser that slides out and flips down over the lens. I understand this. It also has a white plastic card which also pulls out but stays at right angle to the flash lens. Can anyone tell me what this is for?

 

[AliB]

It's called a bounce card. You can point your flash straight up and it will "bounce" an amount of light at your subject in front of you. Saves overwhelming the shot and provides a catchlight in their eyes.

There are several ways of making your own bigger better version too. If you Google "build a better bounce card" a whole world of Blue Peter modifications await your delectation

 

[oldfella]

The perspex diffuser serves two purposes, diffuse the flash and alter the angle of flash. Sometimes called a wide angle adaptor.