A Ground Source Heat Pump (GSHP) allows you to heat your home and hot water without burning anything! The heat pump takes heat from the ground and uses a compressor to make that heat hot enough to heat your home and water. Some systems are reversible, so can provide air cooling as well as heating. Heat pumps have been widespread in Sweden, Europe and North America since the 1980s, but have become more popular recently as they have a very big impact on your carbon footprint.
Gas and electricity prices have shot up recently, but gas prices have gone up more than electricity prices have. As a result, a well designed heat pump system can be cheaper to run than a main gas boiler and much cheaper than LPG or solid fuels.
Ground Source Heat Pump (GSHP) vs Air Source Heat Pump (ASHP)
GSHP operate using a similar principal to ASHP, but in this case use the more stable temperature of the ground as the main heat source via what is known as a collector array.
GSHP used to be much more efficient than ASHP, however this gap is now slimmer and the warranties on offer are similar.
Please see this ASHP article for answers to all of your nitty gritty questions on heat pumps in general.