Making a Book cover
Bleed means that when image elements such as pictures or lines fill up (part of) the board surface without margins, the editing area is set larger than the board surface, keeping in mind that they will be cut off during the cutting process. In simple terms, you can think of it as a negative margin. If the bleed is not held and matched to the board surface, an error in the cutting process may cause a completely unintended band on the edge.
Trim refers to cutting out a part of a picture or photo to fit the printing surface.
Therefore, the bleed size is the size that was edited by making it larger than the actual board with the possibility of being cut off, and the trim size refers to the size of the actual board that remains when the part to be cut is cut to fit the board.
Bleeding is meaningless if you edit with a blank space without any editing elements to fill it up without a blank space. You can edit according to the trim size, which is the actual plate surface.
In the case of coloring or picture books, the edge arrangement, or with bleed setting, is common because the image often fills the entire page of the book.
Here is the examples for making book covers!
Myungja Anna Koh