Is merging and flattening the same thing?

[Komodo]

I know this question has been asked already but I still can’t find an answer.
 
When I formatted my book interior design, CreateSpace said that all my illustrations NEED to be flattened. If I don’t do it they will. I have three illustrations that will be on cream color paper so I need transparency in my images and I can’t find a way to have both transparency and flatten in my image.
 
I did see many suggestions to merge the layers, image -->Merge visible layers.
 
Is merging and flattening the same thing?

[rich2005]

It can be. You can merge 2 layers leaving other layers. Merging all is flattening, that is, producing an image file with only one layer. So exporting to png or jpeg is flattening since these formats only support one layer.

Although in Gimp the layers dialogue menu has a Flatten function. This removes all transparency so do not use that. Similar to exporting to a jpeg.

You need a single layer with transparency? then merge all layers and export to png or maybe psd format.

edit:

Quote:..I have three illustrations that will be on cream color paper so I need transparency in my images and I can’t find a way to have both transparency and flatten in my image....

The other thing to remember when printing is, there is no white ink. Any white in your image is the colour of the paper. You will only need transparency if it is partial transparency.

[Komodo]

Thank you so much rich2005 for your explanation on the process. I now know exactly what to do.