As the name suggests, a smart lamp is a standalone light. Most smart lamps can be controlled through an app. Some allow you to change the color and intensity of the light at will, or even schedule such transitions.
A smart light switch offers many of the same features they are just delivered in a very different way. Such devices replace your standard switches, allowing you to turn on the lights through physical controls or via your smartphone.
Smart lamps are easier to install, but they only light a limited area. In contrast, smart light switches can make your entire home smart.