Pardon me for being an ignorant Brit, but what exactly does the Labor day holiday celebrate?

Nige
The True Meaning of Labor Day
It seems ironic that Americans celebrate labor by taking the day off. Does Labor Day mean nothing more than watermelon, baseball, barbecues and beer?
While we may have forgotten it, Labor Day, in truth, is about celebrating the American worker, who in recent days has come under attack as companies export more and more jobs to foreign shores. Labor Day is a time for everyone to remind themselves of the accomplishments of American workers, who continue to set records for productivity.
According to the US Labor Dept, the annual holiday "constitutes a yearly national tribute to the contributions workers have made to the strength, prosperity and well-being of our country."
The holiday has a rich history.
Labor Day's Founder
More than 100 years after the first Labor Day observance, there is still some doubt as to who first proposed the holiday for workers.
Some records show that Peter J. McGuire, general secretary of the Brotherhood of Carpenters and Joiners and a cofounder of the American Federation of Labor, was first in suggesting a day to honor those "who from rude nature have delved and carved all the grandeur we behold."
But it appears more likely that machinist Matthew Maguire, not Peter McGuire, founded the holiday. Recent research seems to support the contention that Matthew, later the secretary of Local 344 of the International Association of Machinists in Paterson, NJ, proposed the holiday in 1882 while serving as secretary of the Central Labor Union in New York. The CLU was the first to adopt a Labor Day proposal and appoint a committee to plan a demonstration and picnic.
The First Labor Day
The first Labor Day holiday was celebrated on Tuesday, September 5, 1882, in New York City, in accordance with the plans of the Central Labor Union. The CLU held its second Labor Day holiday a year later, on Wednesday, September 5, 1883.
In 1884 the first Monday in September was selected as the holiday, and the Central Labor Union urged similar organizations in other cities to follow the example of New York and celebrate a "workingmen's holiday" on that date. By 1894, 30 states had adopted the holiday in honor of workers, and on June 28 of that year, Congress passed an act making the first Monday in September a legal federal holiday.
Guidelines for the observance and celebration of Labor Day were outlined in the CLU's original proposal for the holiday - a street parade to exhibit "the strength and esprit de corps of the trade and labor organizations" of the community, followed by a festival for the workers and their families. Speeches by prominent men and women were introduced later, as more emphasis was placed upon the economic and civic significance of the holiday. In 1909, the American Federation of Labor designated the Sunday preceding Labor Day as Labor Sunday, which was dedicated to the spiritual and educational aspects of the labor movement.
The character of Labor Day celebrations has undergone a change in recent years, especially in large industrial centers where mass displays and huge parades have proved a problem. However, Labor Day addresses by leading union officials, industrialists, educators, clerics and government officials are still given coverage by newspapers, TV and radio.
The US Dept of Labor notes on its website that "the vital force of labor added materially to the highest standard of living and the greatest production the world has ever known, and has brought us closer to the realization of our traditional ideals of economic and political democracy. It is appropriate, therefore, that the nation pay tribute on Labor Day to the creator of so much of the nation's strength, freedom, and leadership - the American worker
Info from:
http://www.jobjournal.com/article_printer.asp?artid=1241