Logic Pro 9 Logic Customized "widgets"

Hi guys,
just trying to make some customized instrument/people icons for my arrange window (tracks).

I have read how to do it over & over but I don't understand what it means by taking the Alpha channel out of the bitmap?

Any one can simplify this concept for me would be appreciated.
I have a friend who uses the Adobe suite but thet wren't sure what i meant when i asked them.....

Thanks In Advance



well I have hundreds of images that I use, er, jpegs converted to png and mostly no bigger than 120 kb. works well, nothing fancy about it, really.