The name says it all: call blocking allows you to block calls from people you don't want to hear. You just have to add their number to the blocking list, and each time they call, they will be refused access. Your phone will not even ring.
This is a great feature for call management. Many people resort to changing their numbers to protect themselves from unwanted calls. If you are a victim of unsollicited and annoying calls, you no longer have to change number. Just filter your calls allow only those from people you trust, thanks to call blocking.