The entire home revolved around the hearth.Everything from cooking to teaching took place at the hearths side.Even magick was done by the dieing light of the hearth fire.But the hearth was not just a meeting place or a place to cook, it was an alter to the gods of the house and nature.The hearth from time immemoreal has been full of religious importants and to the modern celtic pagan it still is.
For this reason the hearth was protected with charms and spells to make sure that the temple of the home was not to become subject to the intreasts of faeries. One very commen charm in Ireland was to place a besom(broom) befor the hearth. No evil could cross its handle.A nother was to hang a pouch of the last harvested grain over the yowning mouth of the hearth.This also showed ones devotion to Beli or later Lugh, the sun god.
In most house holds, the hearth was also where worship was given to the Gods at the sabbaths.The most commenly worshipped hearth divity was Brigid most likely because of Her assotiation with fire and mothercraft.. The irish "Brid's Bed" was usually placed here, or at least a Grain Dollie, in honor od The Great Mother most usually called Dana or Ana.
So in simliest terms(the best kind)the hearth was the heart of the home.It may also intreast you to know that pagan means heathen and heathen means"people of the hearth."