Almost every chapter 13 plan involves a monthly payment to the standing trustee, which is in turn distributed to creditors. The two primary ways the monthly payment can be made is either by directly paying the trustee (e.g. mailing a check) or by having an employer withhold the payment from each paycheck.
The trustee in a chapter 13 case is a standing trustee who has been appointed to handle a large number of chapter 13 cases in a district, typically in one geographic area. The standing trustee is deeply involved in a chapter 13 case, including collecting the debtor's plan payments and distributing the proceeds to creditors.