These are both random and targeted. "Survey" is also a nice way to put something which is far from that.
Random in that it might be every 40th passenger or selected by a randomizer. Targeted in that you yourself might be on a watch list or that CBP is looking for someone scheduled to enter around the time of your arrival and who fits your rough description.
Bottom line is that CBP could still conduct 100% full inspections and search every bag and person entering.