What is "fraud"? People have gotten in to trouble for accepting groceries from family members and not reporting it to the benefit office as additional (in-kind)

What is "fraud"? People have gotten in to trouble for accepting groceries from family members and not reporting it to the benefit office as additional (in-kind) income. Technically, it is fraud, too, so they're not wrong. There's a long list of examples of "fraud"; like many crimes it's a scale.