What is a star diagram in celestial navigation?

a star diagram is a circle on which we plot the location of stars

the circle represents the sky above and it is divided into 4 quadrants

while knowing the northerly direction we plot the stars with respect to its location from true north

and we tabulate its declination in a separate column

since location of stars for a particular time from a particular geographical position is predictable so we match it and obtain own position in terms of latitude and longitude