Lughnasadh ['Lu ɣ nasað] Celtic, is the third of the four great Irish festivals and is celebrated beginning on the eve of the night before August 1st and on that day. It marks the beginning of autumn. The other three festivals are Imbolg (February 1st), Beltane (May 1st) and Samhain (November 1st).
Lugnasadh marks the beginning of the harvest season and was therefore celebrated with community festivities among farmers.
In neo-paganism, Lughnasadh is one of the eight holidays or lunar festivals in the wheel of the year and comes before Mabon and Samhain. Lughnasadh commemorates the sacrifice and death of the grain god: the grain, initially born as a seedling, which in its "death" nourishes man, is seen as one of the aspects of the sun god.
Some neo-pagans celebrate the holiday by baking an image of the god in the form of bread, which they then consecrate and eat. Some also make bouquets of various grains and grasses and flowers. These are tied together with a ribbon on which they write their wishes and then hung up.
Lughnasadh is often defined as the midpoint between the summer solstice and the autumnal equinox, which is halfway in Leo (for the northern hemisphere) or Aquarius (southern hemisphere). The northern hemisphere's Lughnasadh coincides with Imbolg in the southern hemisphere. As a holiday, it is preceded by Midsummer, while Lughnasadh is followed by Mabon. Neo-pagan Lughnasadh festivals can include elements from a wide variety of traditions.
Neo-pagans also use the term Lammas, which was first attested in Anglo-Saxon times as hlafmæsse »(bread) loaf mass« and refers to the Christian feast of St. Peter’s Chain, where bread made from the first grain cut was consecrated.
Source: Wikipedia