These men are the dregs of Pendor society; with no trade skills and likely not patient enough for agriculture, they have resorted to common thievery to get by, stealing or improvising weapons to do so.
They are poor fighters and poor shots, and really the only thing they might have going for them is raw numbers and their ability to stop a mount with their polearms. Robbers (and their less common tavern-recruitable comrades, the Town Thug,) form the very bottom of both the criminal and mercenary troop trees. They're absolutely pathetic in any meaningful confrontation beyond padding your ranks, and only farmers, refugees, and peasant women are equal to them. For a new player who is acting alone or with the starting sellswords typically available in the tavern at the very beginning of one's adventures, they can be quick source of income in prisoners to sell and poor quality loot. Their weapons are generally non-blocking daggers and butcher knives, torch/club/cudgel, scythes, pitchforks, boar spears, low damage bows and more rarely, both small hand axes and larger two-handed axes.
One pass with a mace on a swift-moving saddle horse is often enough to take them down and net you 20 denars a head, and large numbers can be grabbed up quickly with relatively little harm to the player if they're cautious around those polearms.
This unit is, with the bandit and the undead troops, the most equipment-varied unit available, both in weapons and in armour combinations; even if said weapons and armor are generally terrible. Should you really want to make use of them, it's advised you have them rout off the field and upgrade them as soon as humanly possible with the post-battle xp.