blending & alpha blending in D3D10

hi!

I am trying to learn D3D10, but I'm having some problems.
1. Can you please explain to me what is blending and what is alpha-blending?

2. I have a background image and some sprites. The sprites are loaded from a file, 32bit BMP, and have transparent areas (which is, alpha). the code I wrote, and didn't work, was:

Code:

ID3D10BlendState* pBlendState10 = NULL; D3D10_BLEND_DESC StateDesc; ZeroMemory(&StateDesc, sizeof(D3D10_BLEND_DESC)); StateDesc.AlphaToCoverageEnable = FALSE; StateDesc.BlendEnable[0] = TRUE; StateDesc.SrcBlend = D3D10_BLEND_SRC_ALPHA; StateDesc.DestBlend = D3D10_BLEND_INV_SRC_ALPHA; StateDesc.BlendOp = D3D10_BLEND_OP_ADD; StateDesc.SrcBlendAlpha = D3D10_BLEND_ZERO; StateDesc.DestBlendAlpha = D3D10_BLEND_ZERO; StateDesc.BlendOpAlpha = D3D10_BLEND_OP_ADD; StateDesc.RenderTargetWriteMask[0] = D3D10_COLOR_WRITE_ENABLE_ALL; pD3DDevice->CreateBlendState(&StateDesc, &pBlendState10); FLOAT NewBlendFactor[4] = {0,0,0,0}; pD3DDevice->OMSetBlendState(pBlendState10, NewBlendFactor, 0xffffffff);

Can somebody please tell me why it didn't work, and what it means? I couldn't figure out from SDK documentation how the operation works. if I exchange SrcBlend with DestBlend why does the sprite dissapear, while if it is so it does not? for me Src + Dest = Dest + Src. (operation add). I can't also understand what the BLEND_ZERO, BLEND_ONE, ... are and how they can be used. and how the operations can be used.

please help.