Each device architecture has some dedicated resources for clocking. Understanding the clocking resources for your device architecture can allow you to plan your clocking to best use those resources. Most designs do not require awareness of these details.
However, you can explore alternatives based on the following clocking details only if you can control the placement. You also need a good idea of the fanout on each of the clocking domains. If you decide to exploit any of these clocking resources, you need to explicitly instantiate the corresponding clocking element.