Central vacuum systems have one large power unit, usually in the basement, containing the suction motor and the waste collection tank. Tubing runs from the power unit to outlets placed at strategic points throughout the home.
Homeowners attach a hose, handle, and brush arrangement to the outlet in the room they want to vacuum. The dust, debris, hair, and allergens get sucked up, travel through the tubing, and then deposited in the waste collection tank.
If properly maintained, central vacuums can last 20 years or more, even if, during that time, you have to replace hoses or attachments.
Yes, central vacuum systems are worth the cost in many ways. They're more powerful than portable vacuums, more efficient, and remove more dust, debris, and allergens. They also last longer and can improve a home's resale value, as their convenience improves desirability.