Why do pine trees get knots in them?

Pine trees develop knots primarily due to the growth of branches that become enclosed in the trunk as the tree matures. These knots are formed when a branch dies and its wood becomes incorporated into the surrounding trunk wood. Additionally, knots can also appear from the tree's response to injury or stress, leading to the formation of callus tissue around the damaged area. The presence of knots affects the wood's appearance and can influence its strength and workability in various applications.