Top of your own link mate.

Central heating is defined as a system that provides warmth to the entire interior of a building from a single point, using methods such as hot water, steam, or forced air to distribute heat to various rooms

It requires mechanical means to move the heat.

“HVAC units” is an integral system that can have an ac unit installed on it.

A boiler can be central heat, but it’s not an hvac unit, but it does fall under the broader “Heating/Venting/air condition” that makes up the term.