CEDAR LAKE INSTRUMENTS

An actuator is a device that produces a mechanical action. That's the generic description, but when people mention "actuator" in conjunction with Arduino, they will typically mean a linear actuator... Anything else: solenoid, linear actuator, etc., usually will require an external driver and more wiring. Although there are some linear actuators that have the same connections as servos... You can find these and many, many more enclosures for sale at my favorite electronics distributor, Digi-Key. Note that Amazon also carries many electronics enclosures, but I haven't found enough of a price difference to offset not having reliable datasheets.