In many countries, child support is the ongoing obligation for a periodic payment made by a non-custodial parent to a custodial parent, caregiver or guardian, for the care and support of children of a relationship or marriage that has broken down. In family law, child support is often arranged as part of a divorce, marital separation, dissolution, annulment or dissolution of a civil union and may supplement alimony (spousal support) arrangements.

Definition from http://en.wikipedia.org/wiki/Child_support