Explicit, in writing, means stated clearly and in detail, leaving no room for doubt. The meaning of the text is clear and evident, so, therefore, how do you think an author can convey meanings in their writing? Hint, think obvious.
So the reader can understand what is going on in greater detail so they can imagine what is going on in their heads. They use scientific language to show the subject of the book, science and to give the reader that same feeling