View Weight Painting
Weight Painting is the process of assigning specific weight information to each vertex in a mesh; that vertex may be influenced by one or more joints within a hierarchy. While automated methods for weight painting exist, at the end of the day, you will most likely end up tweaking that output to achieve the necessary behavior. Note that weight painting is slow and laboriuos. Lots of back-and-forth is required, as is a ton of patience. Given all of that, properly executed, the results of your weight painting efforts can really pay off.