There are two main types of baseboard heaters: convection and hydronic baseboard heaters. Convection baseboard heaters help circulate the heat around the room. Hydronic baseboard heaters emit soft heat via oil or water that helps maintain the room temperature when turned off.
Baseboard heaters typically require hardwiring with a separate adjustable thermostat, while portable plug-in baseboard heaters require a standard 120-volt outlet and feature built-in adjustable thermostats.