Simple image masking

[fafayqa]

Can anyone explain to me how to create simple masked image so that the areas that the mask is in white would be fully visible, areas that are black would be fully transparent and everything in between would have its alpha channel according to the amount of gray? Cos when I think I do image masking it in fact just applies the BLACK COLOR to the image instead of making those parts transparent and I am unable understand why in the world it is like that?

[fafayqa]

"Join Image With Alpha" node...ah, my bad! :-)))

[phazei]

omg, thank you for coming back and answering your question, I've looked for a while before and couldn't find that.