Bed Levelling Guide
Filament extrudes thin or not at all in some places, often bulging out in others. Extruder motor might slip / click.
Filament bulges out of the sides of the nozzle which squishes into other lines, sometimes causing a pattern.
Filament is flattened, adheres well to nearby lines, no gaps or peaks between lines.
Filament appears rounded, connection between lines is loose, gaps may appear.
Filament is totally rounded, little to no connection between lines, doesn't stick to bed.