Please explain to me, I can't understand this picture? And probability density?

Probability distributions . The distribution of a variable in the 0.5 whole population is called its probability distribution. 0.4 . For a continuous variable like beak depth, the distribution in the population is similar to a theoretical probability distribution known as the normal 0.3 distribution. Probability density Description 0.2 . The horizontal axis is labeled beak depth in millimeters with points ranging from 6 0.1 to 14 with increments of 2. . The vertical axis is labeled probability 0 density with points ranging from zero point one to zero point five with 6 8 10 12 14 increments of zero point one. The curve is concave down and is bilaterally Beak depth (mm) symmetrical. Whitlock & Schluter, The Analysis of Biological Data, 3e 2020 W. H. Freeman and Company . It starts from the horizontal axis before 6, rises up, peaks at about 10, slides down, and ends at after 14