plt.text(site_coordinate[i, 0], site_coordinate[i, 1], site_name1[i], fontsize="8")

This line of code adds a text label to a plot at the coordinates specified in site_coordinate[i, 0] and site_coordinate[i, 1]. The label is site_name1[i], which is a string variable containing the name of the site. The fontsize argument sets the size of the text label.