Baseboard heating falls into two main categories; room-by-room electric baseboards and central baseboard heating that circulate liquid through the system. Both types use radiant heat, in which cold and warm air is used to create a radiant effect to heat a room. Baseboard heat is better for smaller rooms and is commonly used in apartments and small homes. 

Electric Baseboards

The traditional electric baseboards are individual heaters that each has their own temperature control. Generally situated under a window, these baseboards have electric heating elements that radiate heat out through aluminum fins. The warm air then goes up into the air and cold air is pulled down into the bottom of the baseboard. This is why they are usually placed under windows, to negate the cooling effect of the cold glass panes.  

Central Baseboards

Central baseboard heating still uses baseboards to transfer warm and cold air like the electric individual baseboards, however they use a centralized form of heat. These are whole home heating systems, versus individual heaters. There are two main kinds of central baseboards, hydronic and solar.  

• Hydronic. These systems use hot water as the heating element instead of electric coils. The system is integrated through a boiler tank that pushes hot water through pipes that go into the baseboards. 
   
• Solar. Similar to the hydronic systems, these systems use water or fluid that is warmed and transferred to the baseboards as well. However, they use solar energy as a heat source. 

Basically, all these units will work similar and even look the same, but the energy source is different. These systems are some of the less expensive types of heat to implement, which is why they are so often seen in apartments and commercial HVAC systems.