The answer to 'what does boiler do' is a boiler is a central heating system that heats water and distributes that hot water or steam through pipes to radiators or other heating devices throughout a home or building. Boilers use a fuel source, such as natural gas, oil, electricity, or propane, to heat the water, which then circulates through the system to provide warmth.
Boilers are a common and efficient way to heat homes and buildings, especially in colder climates. They can be either a tankless or storage-tank design, and come in a variety of sizes and capacities to meet the heating needs of different sized spaces. Regular maintenance and professional servicing is important to ensure a boiler is operating safely and efficiently.