Load Bitmap in DB should be read as Load 'Screen' so a DB bitmap is not the same as a Windows bitmap.
When you load a bitmap, you have to supply a bitmap (or screen) number. This is a number between 1 and 32.
When you do, a hidden screen is created and the specified image loaded into it - while you are still looking at screen 0 which is the one which appears on your monitor.
Once the image is loaded, all screen operations - such as Get Image/Paste Image etc - are directed to that hidden screen so you don't see it happening.
When finished, you can use Set Current Bitmap 0 to switch back to working on the main screen and either delete the other bitmap or leave it there to grab more images later on.
You can also use a hidden bitmap screen to build an image instead of loading something into it - for example you can create images for sprites with text on them on the fly and without the process being seen.
If you know the image you want is the correct size, you should use Load Image because it cuts out all the steps outlined above.
TDK_Man