The cheapest robovacs will only have a dock for charging. Pricier models incorporate self-emptying of the onboard dustbin, and draining/refilling of the onboard water tanks. The very fanciest models offer automatic mop pad cleaning, and detergent dispensing for the mopping fluid. For $100 more, you can dispense with dealing with https://www.youtube.com/watch?v=Lhgk6D1ayeM&