A central heating system provides warmth to the whole interior of a building (or portion of a building) from one point to multiple rooms.
When combined with other systems in order to control the building climate, the whole system may be an HVAC (heating, ventilation and air conditioning) system. Central heating differs from space heating in that the heat generation occurs in one place, such as a furnace room in a house or a mechanical room in a large building (though not necessarily at the "central" geometric point).
Such areas normally use gas heaters, district heating, or a oil-fired system, often using forced-air systems.Steam-heating systems, fired by coal, oil or gas, are also used, primarily for larger buildings. Electrical heating systems occur less commonly and are practical only with low-cost electricity or when ground source heat pumps are used. Considering the combined system of central generating plant and electric resistance heating, the overall efficiency will be less than for direct use of fossil fuel for space heating.Źródło: https://en.wikipedia.org/wiki/Central_heating
A boiler is a closed vessel in which water or other fluid is heated.
The fluid does not necessarily boil.(In North America the term "furnace" is normally used if the purpose is not actually to boil the fluid.) The heated or vaporized fluid exits the boiler for use in various processes or heating applications,12 including water heating, central heating, boiler-based power generation, cooking, and sanitation.