Most lenses will allow both autofocus and manual focus, though some may only allow one or the other. In most shooting scenarios autofocus tends to be easier and more accurate, though there are some situations (e.g. video, very busy/detailed scenes, very low/high contrast) in which manual focus often works better.
The focus motor that drives a lens’ autofocus can significantly affect the noise and speed of the lens’ operation. Ultrasonic (aka supersonic, hypersonic or Silent Wave, depending on brand) motors, common in DSLR lenses, are virtually silent and usually fast—huge benefits particularly for wildlife photographers but also those who shoot weddings, sports, action and live performances. Linear stepper motors common in mirrorless (and some DSLR) lenses can provide fast, smooth and silent autofocus while shooting video.