Constraints are a cornerstone of the framework and allow you to control functionality of other operating nodes (similar to Mographs Effectors). You will use constraints in your everyday work as they are really one of the most important components to customize and extent the framework functionality and specialize other operating nodes to meet your requirements. The great thing is that almost all nodes in the framework can use them and that they can be called fully multithreaded. So you better get used to them if you want to create complex setups.