The "schematic" of a project is produced by eeSchema during the first phase of the project development process. You may know "schematics" as "circuit diagrams".
(Yes, you DO have to do a schematic before you start to draw the PCB.)
Here's a very simple example:
(Please don't think ill of KiCad because of the resolution you see there. The poor resolution is an artifact of the screen capture process. Note also: When you are using KiCad, a very elegant system of zooming and panning is available to you.)
(This entry could be expanded! If you particularly want THIS expanded, write and cite "Page co1schem")