This pattern is for mathematically ideal crochet spheres of different sizes! There are 10 different sizes in this pattern. Turns out the number of stitches in each row scales with sin(theta), where theta is the polar angle of the sphere.
Post stitches are fun stitches that add lots of texture to your project. When you need to decrease, here are photo and video tutorials for both the front post double crochet (fpdc) decrease and the back post double crochet (bpdc) decrease.